AN ENVESTIGAHON 0f FIRE ALARM
SYSTEMS AND EQUIPMENT
FBR RESIDENUAL USE

THESES FBR THE DEGREE OF M. S.

JOHN S. SCHEURICH
CLEM A. WOODARD
I 9 3 3

AN IFVESTIGATICN OF FIRE ALARM SYSTEMS AND EfiUIPfiIKT

;

 

FOR

RESIDENTIAL USE

 

A
'L‘l 318 IS

Presented to

The Graduate School
of

Michigan state College
for the

m. S. Degree in Electrical Engineering

W

Clem A; Woodard

East Lansing, Michigan

March 31, 1935

THESIS

 

 

An investigation of fire alarm sysuems and equipment, the complete
results of which, together with descriptive matter and data concerning
a relay and two thermostats, designed and built by us during our study,
-make up, in the fOllowing thesis, a fairly complete survey of fire alarm
equipment adaptable to residential use.

The history of rire Alarms, a part of this thesis, deals with equip-
ment used in past times. Although in preparing it we have covered a
large majority of the current sources of information concerning such his-
tory, it is by no means complete, as much material is not recorded in a-
vailable papers.

ln "rhe hire menace", a section of this thesis, we have tried to
set forth data concerning the losses by fire in residences throughout
the United States. rhis data convinces us that there exists a real need
of adequate, economical fire protective equipment in the home.

with this need and certain practical considerations in mind, we
have attempted to survey the fire alarm equipment available today on the
market which might be readily adapted to this use. After making a
rather complete survey, we believe there is little or no equipment on
the market today which fully meets the requirements, as we see them,
for use in the modern residence. Hence, we have endeavored to design
and construct, as far as possiole, during the time available to this
work, equipment especially designed for residential use.

We regret that the time available did not permit a more complete

survey of the problem. The construction of the relay required more

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time than was at first apparent. For this reason, we feel that,
while substantial progress in the right direction has been made,
there still exists certain facts concerning this subject which are
worthy of further study. In the eonClusions of this thesis we have
set down facts pertinent to the subject which we did not investi-
gate.

J. S. S.

C. A. W.

¥¥A#:?********

AC IQ"? 0‘7." L‘ ID GU71“

 

To Professor L. S. Foltz, Head of the Electrical Engineer-
ing Department of michigan State College, we extend our sincerest
thanks, for his most courteous supervision of this investigation

and his many timely suggestions.

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Page
The Fire Menace — - - - - - ------- 1
The History of Fire Alarms -------- 8

Present Types of Commercial Alarms - - - - 25

Fire Alarms for Residential Use - - - - - 34

Experimental Work ------------ 58

Conclusions - -------------- 92

1.

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It is a well known fact that fire is not a new problem but is one
that has been associated with every civilization. It is time that it
be conquered, and the dangers from such be reduced to a minimum.

The purpose here is to bring out the grave danger of fire to dwell-
ing houses, and the importance of providing suitable protection to re-
duce this to a minimum. A fire in the home is one of the most feared
dangers. At the same time it is one for which there is a minimum of
preparation. To the average citizen, a fire destroying his home means
that he has to start over again. Possibly he has not only lost prop-
erty but some of his family.

The fire menace is more appalling when it is considered from the
standpoint of total losses in property and life. The President's sug-
gestion of an international debt moratorium startled the world because
of the fact that the United States would have to forego the receipt of
a quarter of a billion dollars in principal and interest annually, yet
our fire losses are almost twice this amount for the same period of
time.

A point of much importance in consideration of prOperty loss by
fire is its prevalence. There has been a startling increase in the num-
ber of fires in residential property. Since 1924 dwelling losses have
increased fifty percent. Poor construction, lack of fire stOpping par—
titions and walls, substandard chimneys, combustible roofs and insuffi-
cient protective equipment are the leading and contributing causes of
these fires. The dwelling losses in 1924 amounted to one hundred six

million, four hundred eighty-two thousand, eight hundred ninety-seven

2.
dollars (filOo,482,897) and in 1930 totaled one hundred fifty-nine million,
eight hundred fifty-three thousand, twenty-four dellars ($159,803,024) or
an increase of fifty percent. Dwelling losses in 1951 were thirty one
percent of the total loss of the nation by fire.

Let us consider this loss to bring out some very important facts.
Take as an example, the loss due to dwelling house fires for the year
1950. This means that each day there is an average loss of four hundred
thirty-seven thousand, five hundred dollars ($457,500). Consider the cost
of an average home as ten thousand dollars ($10,000); this means that near-
ly fifty homes are destroyed daily by fire; each day fifty families are
turned out homeless and many with nothing left with which to rebuild.
This is by no means an easy problem to solve and will, of course, take
time but action in the near future is imperative. If conditions are left
as they are, by 1956 our dwelling losses will amount to two hundred forty
million dollars (240,000,000) or a quarter of a billion dollars.

As a final thought to fix in our minds the great property loss due
to fire consider the following table furnished by the Lansing Division
of the Boston Insurance Company. This gives the annual fire loss in the
United States for the last fifty-seven yearS, that is, from 1875 to 1951
inclusive. It is well to keep in mind that in the last ten years, even
though the total loss has remained the same, the loss due to industrial
concerns has decreased and the loss due to residential or dwelling fires
has increased, the impressive total being half a billion dollars annual-
ly. In order to reduce this waste of value, it is necessary to provide

suitable protection in the way of residential fire alarm systems.

Annual Fire Loss in the United states for Fifty-seven

years. 1875-1931, inclusive

Year Aggregate property loss
1875 $78,102,285
1876 64,630,600
1877 68,266,800
1878 64,315,900
1879 77,703,700
1880 74,643,400
1881 81,280,900
1882 84,505,024
1883 100,149,228
1884 110,008,611
1885 102,818,796
1886 104,924,750
1887 120,283,055
1888 110,885,665
1889 123,046,833
1890 108,993,792
1891 143,764,967
1892 151,516,098
1893 167,544,370
1894 140,006,484
1895 142,110,255
1896 , 118,737,420
1897 116,354,575

1898 150,595,905

Year Aggregate property loss

1899 _ $153,597,830
1900 180,929,805
1901 185,817,810
1902 161,078,040
1905 4145,502,155
1904 229,198,050
1905 155,221,550
1908 518,611,800
1907 215,084,709
1908 217,885,850
1909 188,705,150
1910 214,005,500
1911 217,004,575
1912 208,458,900
1915 205,785,550
1914 221,459,550
1915 172,055,200
1918 258,577,952
1917 289,555,050
1918 555,878,878
1919 520,540,599
1920 447,888,877
1921 495,408,012
1922 508,541,001
1925 ~ 535,372,782

1924 549,052,124

Year

1925

1926

1927

1928

1929

1930

1951

Aggregate property loss

$559,418,184
551,980,751
472,955,989
464,607,102
459,445,778
501,980,824

464,633,265

5.

6.

There is also a humanitarian viewpoint in consideration of the fire
menace. The loss of property, however. appalling or enormous, cannot be
compared with the needless loss of lives by fire. The annual toll of
lives due to fire is fifteen thousand, which sounds even more astonishing
when we find that this toll is larger than forty-one lives daily.

This loss in lives should be materially reduced by the application
of every known means for preventing and extinguishing fires. In the ex-
tinguishment of fires time is of major importance. One minute may mean
the loss of control of a fire. A reliable alarm reduces the factor of
time to a minimum and gives firemen the maximum advantage, thereby reduc—
ing all losses.

If one gives thought to his home it is always his utmost desire that
it be protected from all danger, especially that of fire. Protection from
fire has always constituted a part of man's necessity. For example, con-
sider the following precautions listed in an article on Fire Protection
from the Annals of The American Academy of Political Science for Septem-
ber 1905.

"It is, therefore, seen that to use reasonable precaution against
the conflagration hazard, we must:

1 - Curtail the size of risks so they cannot contain in any section
an amount of combustible substance, which, if on fire at one time, is
likely to place the district beyond control of existing facilities.

2 - Extend over most occupancies, the protection of a well designed
signal system.

3 - Positively prevent communication from floor to floor of a build-
ing except through fire proof shafts.

4 - All exterior windows, including all windows on the street front,

7.
except outside open areas, should be fitted with fire proof wire glass
windows and, when exposures are severe, with approved shutters also.

5 — The public water and fire department facilities, in most in-
stances, poorly prepared to meet severe conditions, should be radically
increased. This may involve the introduction of a modern, adequate and
direCt fire pressure water supply."

Some such program might well be outlined for the protection of resi-—
dences which would necessarily reduce the large annual 1083 due to fires.

In the present day, fire departments are equipped sufficiently well
to quench fires if some suitable means of notification, dependable at all
times, is installed in our homes to maxe the presence of fires known
promptly. Thus there is necessity for residential fire alarms wholly
applicable to all homes and financially available to the average working
man.

Not only is it desirable to have fire alarms for the protection
they offer but it is also important from the standpoint of insurance
rates. These rates are based on fire danger. A definite value is placed
on all fire protection measures, based on tests and trials by the under-
writers with a close study of records and observation of actual operation.
Insurance companies reduce their rates where suitable fire alarm signal
systems are installed.

In conclusion it can be said that there is a necessity for a resi-
dential fire alarm system to reduce the annual one hundred fifty million
dollars ($150,000,000) prOperty loss, to prevent the needless loss of
lives in dwelling house fires, to provide absolute protection from fire

and to ultimately lower the insurance rates of home pOIicy holders.

8.

THE HISTORY OF FIRE ALARMS.

The purpose of the following pages is to give a brief review of com-
mercial fire alarms that have been developed in the past. This will in-
clude not only devices that might be suitable for residential use, but
also all phases of fire alarm development.

In a history of fire alarms it is rather difficult to pick any parti-
cular time from which to start. The earliest means of fire fighting was,
of course, by means of the ladder and bucket brigade. As time progressed
the necessity for a more dependable method of fire fighting was necessary.
Probably the next step in the development was that of a gong arrangement
and the well known fire wagons drawn by horses. The horse drawn fire
wagon was durable and fairly efficient and served a long time. During its
stay several methods were devised for notifying the fire department of a
fire. During the last decade the horse drawn fire wagon has been entirely
replaced by powerful and fast automotive fire wagons. Several fire alarm
devices were developed and put into use, and we wish to give a review of
the develOpments of this time. We will first consider some alarm devices
that later formed an integral part of a general alarm system. Secondly,
we will consider the development of the alarm system used in some larger
cities of the United States and a review of their present status. Last-
ly, we will consider briefly some alarm systems used in foreign countries.

In 1906 two types of fire alarms were developed, one by a scotch in-
ventor and the other by a Dane. The former was of the automatic sprinkler
type. This device rings an alarm, and starts an automatic sprinkler
which acts as a first-aid appliance while waiting for the arrival of the
fire department. In case of a sprinkler head becoming damaged, there is

no danger of flooding the premises because in this system there is neither

9.

water or compressed air in the sprinkler pipes when they are not in use.

In three tests on this sprinkler system, the results were very satisfactory
and each time the fire was readily extinguished, in most cases before the
fire brigade arrived from a distance of one and one quarter miles.

The Danish invention was of a different type and is confined to the
ringing of the alarm bell. It is a very sensitive device and acts only
on the application of a sudden wave of heat. The appliance consists of
a U-shaped tube four inches in height filled with mercury. The upper parts
contain sulphuric ether, and both ends are closed. One side of the tube
is covered with non-conducting material. The device will not operate due
to a gradual rise of temperature, whereas a direct wave of heat such as
caused by a fire coming in contact with it causes the ether under the ex-
posed glass to vaporize, forcing the mercury down which closes a circuit
and rings an alarm. The chief objection to this device is the Open cir-
cuit Operation.

Around 1900, two American inventors, Siemens and Halske, invented a
fire alarm device for notifying the engine house of the fire. It consisted
of a clockwork system which was enclosed in an iron box to protect it
against the elements and bad treatment. The person giving the alarm could
start the clockwork by means of pulling a handle on the outside of the
box. A message would thus be sent to the engine house. The telegraph
apparatus placed in the engine house would write several times upon a
tape the message or sign transmitted, while a bell would give the alarm
to the firemen. The firemen had only to compare the sign described by
the telegraph with those of a tablet placed above the apparatus in order
to ascertain the source of the alarm. In order to permit this alarm

l>eing easily found at night a lamp provided with a red glass, to easily

10.

distinguish it from other lamps, is supported on the alarm box. A re-
flector illuminates the handle of the alarm and the directions for mani-
pulating it, with a brilliancy equal to that of daylight.

Dissatisfied with the faCt that this apparatus had one defect which,
of course, was that of the intervention of man, these two American in-
ventors, in 1903 invented a simple automatic alarm system. The most im-
portant part of this alarm was a thermometer tube, the bulb of which holds
a spring switch out of contact. When the temperature rises, the bulb of
the thermometer bursts, and the spring is released thus closing the cir-
cuit. The closing of the circuit gives an alarm in the engine house and
if desired also a local alarm.

An automatic chemical fire extinguisher, very novel in design, was
invented in 1902 by Mr. Louis Wirlum of Elsmere,beleware. The device be-
longs particularly to that type in which a liquid is precipitated from one
receptacle into another for the purpose of generating a gas fatal to com-
bustion.

At Brussels, on the 26th of July 1902, nmile Guarini carried out
SOme practical experiments with a fire alarm device invented by himself.
This possessed the peculiar characteristics of notifying the engine houses
automatically not only of the existence of a fire, but also of the name
and the position of the building in danger of destruction. The mechanism
of this device consists of a wireless transmitter and a wireless receiver.
The transmitter is actuated by means of a mercury thermometer. The heat
of a flame of fire causes the mercury to rise and make contact with a
platinum wire inserted in the upper end of the tube of the thermometer,
and thus closes an electric circuit which, by means of several mechanical
devices, transmits the necessary message to the wireless receiver at the

engine house.

ll.

Along this smue line of Wireless telegr.pny for transmitting fire

alarm s :nals comes the use of telephone li es for automatic fire alarm

(ff-

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systems. This alarm uses telephone lines without int rfering with the
normal functioning of the phone system. it was designed for use in hotels,

factories, mines, and public buildings, and for calling volurteer fire—

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men in towns that have VOluntCOr fire department . Considered in
broadest uscht this alarm system consisted of a rotating switch, operated
by Spring motor wI-iich autorgicitical 1;; 06:11:33 bells to ring; in differ-int
circuits, a different number of times as a fire signal.

A little earlier than the previous alarms discussed is one pvt out
by the Goldstien r re-hlann'relegr p} system in 1395.

Assentially the system consisted of three parts, a thermostat whic;
acts unde‘ the influence of heat, an anni;cistor, which receives the alarm
from the therwestut and iidicmtes it by visual signal, and bell signa .
;he visual signal ifldiCptuS the floor and room where the fire has been
netected. rue s’stem also consists of a transmitter which transmits the
alarm by wire to a car din fire station.

The theniosi t consists of a hollow cylinder in whine is located a
washer of asbestos coated with Jareffine. Geneath the washer lies a

loose i‘i tii'g piston which receives tne pressure of a special 3

The syrinv is held under cemwression by a red, the lower end 0” which is

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ruatairuyi byr'two .uiles (n’ s.rlisl:. ;€uese rIisks :u"e luali thp t u:r «it a
solder “H.UflllflClES at u tezhmufivburu of 1000.

trim; axuiwixziattez' coxrtaiiis zi clxvclnvorig, VfiliCll{lutiflfitlllc.gll;’ stzr~ts a;
bell ringing device both locally and in the fire Stdoluu. The clocbmark

also Operut;3 shutters in such a manner to indic;te the exact location

Of the fire.

12.

The transmitter consists essentially of a magneto-electric machine,
impelled by a weight which is released by an impulse of air from any
thermostat in the building. The transmitter is also electrically con-
nected with the central exchange of the local telephone company.

The thermoscope, a fire alarm device invented by Mr. Eugene Gar-
retson in 1913, is an appliance in which the active element is a substance
having a negative coefficient of electrical resistance. The thermoscope
forms part of an electric circuit which also contains an alarm gong arrange-
ment and an indicating device telling where the fire is located. At normal
temperatures the resistance of the active element is high and the current
passing through the circuit is not sufficient to work the alarm. When the
temperature of the air surrounding the thermosCOpe rises to a certain de-
gree, due to the heat from a fire, the resistance of the active material
drops so as to permit the passage of sufficient current to give the alarm.

In most of the earlier automatic fire alarms, thermometers were ar-
ranged to close an electric circuit when a dangerously high temperature
occurred. This type of alarm met with very little approval because it
was likely to be Operated when there was no fire, by means of an accumu—
lation of heat in some badly ventilated spot. Also it quite often failed
to operate when there was a fire until it was too late, merely because
the temperature at the particular point where the automatic device was lo-
cated did not happen to rise to the point for which the device was set.

It was due to this that an American inventor, in 1910, designed a device
which overcame these difficulties. This appliance Operated to close an
electric circuit where there is a sudden rise in temperature. It consisted
of a metallic chamber which forms an air reservoir, and in case of a sudden
rise of temperature the air is rapidly expanded and causes a contact ter-

minal to rise and make contact with another. This 010863 an electric

l3.

circuit to a bell or sprinkler or, in some cases, to both. The device
will not operate due to a gradual rise in temperature, because the air
expands very slowly and escapes through a small tube, thus preventing
closing the contact terminals.

Another fire detector that is based upon the expansion of compressed
air was invented by Charles H. Hayser of Newark, New Jersey in 1916. It
was about the size of a shot gun cartridge, and the results of numerous
tests conducted with it under service conditions disclosed the fact that
it was a dependable means of detecting conflagrations. This detector is
the electrical contact-making member of a fire alarm system. One circuit
will take care of as many detectors as may be necessary to cover a given
premises. This appliance depends for its operation upon expansion Of a
small quantity of imprisoned air. Like the above air reservoir type de-
tector it is Operated only by a sudden rise in temperature. It is also
claimed that this device will work equally as well in ice houses, boiler
rooms, or other places where abnormal temperatures are maintained for
commercial use.

In 1920 William J. Luce, a fireman Of New York City developed a fire
alarm system which automatically telephoned its message to central, and
thus to the fire house. Briefly the system consists Of the use Of thermo-
stats located at intervals of twenty-five square feet or one for every
room of the premises to be protected. These thermostats are placed in a
circuit supplied with current by one or two dry cells. As soon as a fire
breaks out in any part of the premises protected with these thermostats,
the battery circuit is closed and, by means of electromagnets, the calling
apparatus is set in motion. The release of a weight, by means of the

energized electrO-magnets, serves to lift the telephone hook, and starte

a phonOgraph. The record on the thonograph tells where the fire is,
street, house, floor, and room if nGCGSSmr , and repeats the message
several times, assuring transmission of the message to the fire station.

The Gamewell Fire Alarm Telegrap COmpany of newton Upper Falls,
hassachusetts devised a compress:d air fire alarm Siren. This Alarm
Siren consists of a Diaphone, a compressed air reservoir for supplying
the power to blow the Diaphone, a motor compressor to furnish this com-
pressed air, and a special electrically Operated valve which Operates
the Diaphone when a street box is operated.

where is very much in favor of this style air compressed system over
the older systems.

First, it has greater volume of sound and greater carrying capacity.

second, the space occupied is much less.

Third, one reservoir will do as efficient work as two or three re-
servoirs of the Old style.

Fourth, it has a distinct ve tone which cannot be confused with the
tone of any whistle or 0th r device.

It might be well to bring out here that this type of Siren is the
most widely usxd to-day. At least fifty percent of the fire sirens used
to-day are made by the Gamewell Fire filarm Telegraph Company of newton
Upper Falls, Massachusetts.

An earlier type of fire alarm for the purpose of a general alarn for
a small village was a gong arrangement. lt indicated according to the
number of strokes, where the fire was located. The bell was mechanically
operated by a special lever arrangement.

The next few pages of discussion will be devoted to the development

of the fire alarm system in New York City. BriLfly, the main advances

15.

and reasons for the advances will be pointed out, along with a discussion
of each.

In l8b5 the fire alarm plant consisted of twelve bell towers or look-
out stations located at points of advantage, "3he mode of operation was
to watch for smoke or other indications of fire with a telescope and to
signal by means of the Horse telegraph directly to the central office.

The primitive system was soon found inadequate and in 1870 a complete
new installation was made at a cost of p150,000 including about 578 street
alarm stations. rhe records of the department show that few difficulties
were experienced for a period of ten years, and in fact many decided im-
provements in its working were effected. This system of installation is
the basis of the present day telegraph plant in the borough of Manhattan.

This system lasted with very few changes until about the year l900.
It then became apparent that it was necessary to make some very decided
improvements, principally because New fork was growing very rapidly and
the equipment on hand was not of sufficient capacity, besides being rather
make-shift and obsolete. The dangers from fire and the losses due to fires
were rapidly increasing, and it was thus necessary to begin action for an
improvement of the alarm system. in use. A movement for an improved sys-
tem started in December 1904. In 1905 the Merchant's Association, the
larger business interests, and several other organizations convinced the
people that there was great need for improvement in the fire department.
we finally convince the people of this fact, the new iork board of Fire
insurance Underwriters condemned the existing system. In march 1907 pre-
liminary plans were formulated for a new fire alarm system but no immedi-
ate work of reconstruction took place until 1911.

rhe new system called for a central fire-alarm telegraph station in

a building abSOlutely fireproof and devoted to no other purpose; a

16.

building which neither fire nor flood could damage. It was erected in
Central Park in a place very much isolated. The telegraph and the tele-
phone wires of the system were laid in underground ducts or subways, care-
fully protected throughout their courses from high tension or from possi-
ble contact with power circuits. The distribution of circuits was planned
systematically as regards the territory served. The boxes were of the non-
interfering type so that every signal would be recorded clearly whether
sent in alone or-simultaneously with other alarms.

It would be well to take time here to explain the old type street
alarm boxes and the improvements brought about in developing the non-in-
terfering type used to-day.

The making and breaking of a circuit for sending an alarm signal from
a box, in a fire alarm telegraph system, is produced by the revolution of
a disk notched in its circumference, so as to provide teeth which engage
a follower, Operating the circuit-breaking mechanism proper. The number
and spacing of the teeth on the circumference of this disk give the signal
for the individual alarm box, and thus indicate from whence the alarm
comes. For example, consider the signal "123" being sent into the central
fire station. In this case there is one tooth, followed after an interval
by two, and after a second interval by three. This wheel or disk is caused
to Operate or revolve by clockwork when the handle on the street box is
pulled by the person sending in the alarm. It makes a certain number of
revolutions thus assuring that the message will reach the central station
fire department headquarters. The circuit thus broken and made by the re-
volving disk affects a sensitive relay at headquarters, and this actuates
a second circuit. The recording and indicating mechanism are connected

in this second circuit in such a way that certain gongs or sirens can be

l7.

operated and certain fire houses notified.

With several boxes on the same circuit it is quite conceivable that
two or more boxes might be pulled at the same time, and the signal either
be totally destroyed or come in badly jumbled. In case the circuit is
broken no signal would be transmitted at all.

In the new New York box developed by Mr. Day and Mr. E. A. Faller,
the first revolution of the wheel is a test to determine whether the cir-
Cuit is so the message can be sent out. If it is perfect the ordinary
transmission of the message takes place over the metallic circuit. If the
circuit is faulty the line is automatically grounded on the side where the
fault occurs and the signal is thus sent to headquarters through the ground
and the one good metallic conductor. This is accomplished by having an
armature released after a single revolution and ¥§EE=a snap switch connect-
ed to the circuit of the ground. In the meantime the operator at headquar-
ters has received a danger signal telling him that a certain circuit is
broken. he then closes a knife switch, putting on the particular box cir-
cuit indicated a powerful split battery sufficient to overcome any resis-
tance so that the current interrupted at the box can be returned through
the ground, and the signal received at headquarters in the usual way.

Another improvement of the new box is the fact that it is interchange-
able, and it is remarkably simple in its construction.

New York is to-day well equipped with street boxes of this type and
with an entirely m0dern central station. Also in the present system the
one thing that was neglected in the earlier systems is the fact that there
is chance for expansion and still maintain the old circuits in their pre-
sent manner.

At about the same time the non-interfering street box alarm was

developed in New York City, another big step was being taken in fire

18.

protective methods. This had to do with wireless telegraphy. Soon after
the successful application of wireless telegraphy to moving trains for
signalling, it was announced that it would be used in the fire alarm tele-
graph bureau for the City of flew York with it's extensive water front and
large shipping interests. Tests were made on an installation at Fire head-
quarters, whereby an operator at the central station of the telegraph
bureau was able to maintain communication with a fleet of fire boats as
they proceeded about the waters of the harbor in answering an alarm or when
' are in actual service, as for example, at a ship on fire at anchor.
This equipment involves a simple installation of wireless apparatus at
Fire headquarters in Last Sixty-seventh Street. There is similar equip-
ment for the fireboat, which so long as it remains at its station is in
touch with the telegraph bureau by fire alann telegraph and telephone.
The apparatus installed had at that time an effective working range of
about twenty-five miles, and was capable of being tuned to any frequency.
ln the paSt few years this equipment has been largely replaced by radio
which, of course, makes the plan even more effective. lt is through
such plans that the great wager front interests are protected.

Thus we see that the fire alarm system of new xork has been constant-
ly changing to meet the required needs for more protection in genera .
Such has been the case in several other cities of the united states. lmong
them is Birmingham, Alabama, where in 1921 a complete modern fire alarm
system was installed.

The system consists of two hundred fire alarm boxes on the street,
twenty-five miles of underground Cable, with a total length of 506 miles,
Zlb miles of overhead wire and a complete new central office which is

fireproof in every respect..

19.

The fire alarm boxes are so arranged that the chief or any of his
assistants can go to the nearest box, plug in a special telephone set
which is carried in the chief's car, and talk directly to the Operator at
fire headquarters. The alarm boxes are all on thirty circuits, the twenty
engine houses are on ten circuits, and all the different circuits end at
the central station.

The signals can be handled at headquarters in three different ways,
automatic, semi-automatic, and manual. If the alarms come in only one at
a time the automatic method is used, or if they come in a little oftener
the semi-automatic method is used, and when they come in rapidly the manual
Operation is used.

There are three separate means provided for sending signals to the
engine house. A register and sounder are mounted on the disk in the en-
gine house, where a man is on duty and signals are received from the cen-
tral office. A loud sounding gong is connected over a separate circuit
to waken the firemen at night. If an alarm is received that does not call
out that particular engine house the man on duty Opens a switch which si-
lences the gong and prevents awakening the firemen. In case of a small
fire, telephone facilities are used to send out a particular company de-
signated for such duty.

Accurate and automatic records of all alarms received and sent out
are kept at headquarters. The box numbers are punched out on the register
tape. This data along with time stamps, which record the day, hour and
minute, furnish a permanent record for reference. The stamp registering
device automatically takes care of the long months, short months, and

leap year.

20.

Back of the central office room, in which all the switchboard and
control circuits are located, is a special room for storage cells which
provide the current. There are 1800 of these cells to provide the energy
to operate the system and furnish a reserve source in case of breakdown.

The fire alarm boxes on the street are of the Peerless, non-interfer-
ing type. Each circuit usually has ten or a dozen fire alarm boxes on the
same circuit. Quite often two different boxes will be pulled at about the
'smne time for the same or different fires. if these boxes interfered with
each other neither message would be received with any accuracy. In case
one box is Operated while another box on the same circuit is sending in
its signal, the second box will not interfere. At the end of each round
'the second box will test the line to determine if it is clear, and when
it is cleared it will send its signal thus not interfering with the first
signal.

Along this same line of fire alarm developments in different cities
is that of the system in Nashville, Tennessee. This system is quite re-
cent in design being entirely improved in 1951.

A new fire alarm building to house the fire alarm equipment is lo-
cated away from power lines of the city in a district free from any inter-
ference. The equipment is Gamewell made, and manually operated. It con-
sists of a thirty circuit control-board, and has some of the most improved
modern equipment. One hundred additional new improved fire alarm boxes
have been installed.

The fire department makes a quarterly inspection of all buildings and
districts of prominence. This work is done by eighteen selected men from

the fire department. The perdistent inspection work and following up of

21.

all hazards it is believed has been directly responsible for a great por-
tion of the reduction in fire losses that have been achieved. For the

year 1930 the reduction in fire losses in the city of Nashville was between
$400,000 and $450,000.

Another fire alarm control system that has received a great deal of
attention in its development is that of Fort Worth, iexas which was com-
pleted in 1951.

The total value of this fire department including land, buildings,
and equipment is ml,5b0,000. A total of two hundred seventy-one men and
officers are employed, and twenty-four companies occupy twenty-one fire
stations and man thirty-six pieces of motorized equipment.

In the fire department repair Shep four mechanics are constantly
employed repairing and rebuilding apparatus. A well organized drill school
with first class tower equipment is maintained to assure the city of a
well-trained fire department personnel.

The fire alarm apparatus was designed, built, and installed by the
Gamewell Company, and is the latest type of fire alarm design. Leading
into the central station office are twenty-three miles of underground cable,
and seventy miles of overhead fire alarm wire, to which are connected four
hundred eleven.Gamewell street fire boxes.

We have thus far briefly covered some of the developments in the field
of fire alarms, and also have showed how some of the fire departments in
different cities have develOped up to the present time. To show a compar-
ison between fire alarm methods in the United States and some foreign
country it will be well to discuss some developments in Germany along this

line.

22.

The German design of fire alarm system is somewhat similar to that
of the designs in the United states excepting for minor details. The
street alarm boxes are designed for Open circuit Operation, that is, when
the circuit is broken the alarm is given. This is accomplished by a
clockwork which is caused to be put in motion by means of pulling a lever
or some such device. The signal is usually a certain number of gongs of
the alarm bell made by a certain number of interruptions of the circuit.
These interruptions are caused by the toothed edge of the disk in the
rotating clockworx of the boxes. :here are usually from ten to twenty
boxes on a single series loop and thus the number of signals or circuit
interruptions vary from one to twenty for the different boxes. When the
message is received at headquarters (usually a central station where the
fire department is located) it is only necessary to refer to the chart
and cenpare the signal received with those recorded to determine from
whence the alarm originated. This method is used in the smaller cities
where a volunteer fire department is the sole support in case of a fire.
Thus as soon as the alarm is received at fire department headquarters the
man on duty immediately sounds a fire siren to arouse the general public.
The siren is so designed that the location of the fire is designated by
the number of signals from it.

Larger and more elaborate street a are boxes are used for the larger
cities. rhe box is very much li”e a clock case and is about two and one
half feet long by one foot wide. lt is provided with a large door ant a
small button with a glass pane, of about one sixty-fourth inch thickness,
over the button. rhe purpose of tiis glass pane is to prevent false
alanns being turned in, it being necessary to first break the glass, (the

breaking of the glass being a damage to property except in case of fire)

23.

before pushing the button. Inside the box, in addition to clockwork,
there is a lightning protector and contact key. The‘key is employed by
the firemen for special purposes in calling the central station. There
is also a loud ringing, mechanical, vibrating bell placed in these alarm
boxes. This is released and allowed to ring for a certain length of time
when an alarm is given. The purpose is to notify those passing by and
the occupants of the burning structure that there is a fire.

.As a receiving apparatus for this system, the direct indicating ap-
paratus has proven itself very reliable. The indicating apparatus is
mounted on the wall, or some such accessible place, in the central station
and enclosed in a case with a glass front. In back of the locked glass
door there is a signal annunciator disk and a line relay which transmits
the incoming signals to the actual indicator or pointer system, the dial
of which shows the various box numbers. There must be the same number of
'indicating devices as there are circuits in the system and the face of the
dial in the indicating case is numbered with the number of street alarm
boxes on that circuit. When an alarm is sent in by Operating one of the
street boxes the pointer on the dial starts moving around and stops at the
number corresponding to the number of the box from whence the alarm was
sent, thus locating the fire. When the indicating apparatus starts in
motion, due to the incoming signal, an alarm is sounded to arouse the fire-
men or at least call their attention to the fact that there is a fire.
This alarm is stopped only by Opening the indicator case and returning the
pointer to its original place. In case that all the firemen are not housed
in the fire department headquarters a special alarm is sent directly to

their home. No general public alarm is sounded because of the excitement

it would cause in a large city.

In conclusion it can be said of the above German fire alarm system
that it resembles very much the system used in the United States except
for minor details. We have brought out the most important developments
of this kind and have given each a brief discussion to show that in the
past there has not been devised alarm equipment suitable for use in resi—

dences in the United States.

25.

PRZSJHT TYPES CF COEMERCIAL ALARMS

Thus far we have shown the need of a residential fire alarm system
to protect the homes of the United States, and given a brief discussion
of the history of some of the fire alarm developments in the past. The
purpose of following pages will be to bring out some of the present
types of commercial alarms.

In a discussion of this kind it would be rather difficult to touch
upon all the phases of existing systems. Thus in the material presented
it will be our aim to present the developments of several of the more im-
portant present day devices used in signal systems.

Among the several companies providing signalling apparatus is the
Howe Signal Company of Chicago, Illinois. The recorder is an automatic
device for recording messages transmitted electrically from various loca-
tions to the central station. This recorder has the particularly important
feature that the cede signals are interpreted in clear type giving loca-
tion, date and time. This prevents any mistakes being made in decoding
the signals. The transmitter is a self contained unit used in conjunction
with various types of actuating switches for all purposes of protective
signalling. This transmitter and switching device can be used to transmit
fire alarms or any other type of signal. The Howe Transmitter has three
distinguishing and important features. They are non-interfering, which
prevents any confusion of signals; they are successive when two or more
are Operated simultaneously; and they are repeating for special kinds of
service, especially that df fire alarm.

The Howe Signal Company provides a special type of panel for control

of all messages sent out by the transmitter. It is interposed between

20.

the transmitter and the recorder for circuit supervision and overload pro-
tection. The unit is entirely self-contained in a steel cabinet fitted

for wall mounting. Careful design provides for full visibility of Ope‘atinj
parts and easy access to the interior.

Among the manually controlled Here Signalling devices is the hire
Alarm Hex. it is of the break g ass type and for Operation all that is
necessary is to break the glass. he further action is required and the
cede signal alarm selected for the particular box is transmitted to the
fire department. The signal is repeated continuously until the glass is
replaced or in some designs it is repeated only a certain, preieterm ned
nmflnn‘of times.

In the supervision of automatic sprinkler systems the llO‘Cse tsigxal
Company has devised some particularly important devices. The flow indica-
tor is an alarm appliance for detecting the flow of rater in the automatic
sprinkler system. nowe Supervisory Swit;hes are automatic devices used
to detect the abnOrmal conditions of liquid levels, temperatures, pressures,
connrel valves and electric circuits.

Howe Complete Systems consist of any of th se Various sigialling de-
vices, suitable control panels and alarm units incorporated into a complete
alann system.

The Gamewell Company of Newton, Massachusetts, is the manufacturer of
several devices applicable to fire ala m systems.

The Gamewell Diaphone is a compressed air siren for the purpose Of
notification of a fire. it is particularly useful for a public alarm where
volunteer fire departments exist. The Diaphene sounds a definite number of
times rhich gives the location of the fire thus allowing volunteer firemen
to go direct to the fire. The fact that it Operates on compress d air

makes it very applicaule to any place since a compressed air unit for its

Operation can be easily installed.

.3

47.

1‘

The Dualarm is another Unmet-1311 product. It is (£33 1;,‘1'1606‘8 _.Jecially

J-‘
I

for puhlic schools. This a arm device ets its nzlme from .ne fact that
it performs two functions simultaneously, that is, it empties the school
of children by supplying sufficient alarms in all parts of the building,
and it calls the municipal fire department at the same time without pull-
ing a separate OOI. in other words the Operation of one of the nemote
ContrOl boxes, for use in case of fire, trips the municipal Fire Alarm
Box and at the same time trips the relay which Operat s the contactor and
ring 8 the local bells.

ihe Three-Fold damewell fire alarm boy for industrial plants, rail-
road propelty, and so lorth is another Guwsvell prouuct. ”his box has no
particulgr features except the fact that it insures Operation even if there
is an Open circuit in the line. In such a case a mechanism trips a switch
and c ans es the open circuited part of the line to the ground thus afford-
ing a complete circuit and assurance of the signal being transmitted.

Another device that the Gamewell Company manufactures is a nockwood
Sprink-La-stat. In afire ale rm dete Mtilfi circuit there is placed a mas-
ter model fire alarm box similar to the Dualalm disc crised above. In the
sane circuit nockw00d sprink- n-Stats are placed and in case of a fire the
master box is automatically Operated by a detecting device (thermostat).
This performs two functions that of Starting the sprinklers and notifying
the municipal fire alarm central station thus calling out the fire depart-
ment. This assures first aid in quenching the fire aid has proven to be
a very successful device for use in induer1tl concerns where the water
from the sprinkl r system can do very little damage.

'rhe holtzer-Cabot Electric Company of Doston, iias sachisetts is 0 con-
cern that develOQS alarm equipment for use in schools. Three principal

systems are in use.

28.

rhe first is for schools in cities or towns where a permanently
manned fire department is maintained. whis is a dual system by means of
which fire alarm signals may be communicated simultaneously to the school
and to the municipal fire departments. In this system fire drills may be
sounded without any danger of calling out the fire department. rhe system
consists of boxes for the purpose of sounding the alarm. These boxes have
a glass panel in the door and in case of a fire the glass is broken and
the inside lever pulled down as far as it will go. This process not only
gives the alarm in the school building but gives a general alarm to the
municipal fire department. in case it is desired to have a fire drill only
the outside door is Opened by means of a key and this disconnects the fire
department. rhe operation of pulling the inside lever gives the alarm in
the school building only.

In places where there is no permanent y manned fire department, a
second type of alarm is used. This system has all other advantages of the
above mentioned system and the station boxes are Operated in much the same
way except that in case of a genuine fire the breaking of the glass causes
the outside door to Open and give access to the lever for Operation. in
case of a fire drill the box is Opened by means of a key.

The third system is one designed for smaller schools and districts
where the cost is a determining factor. This system has no connection
with the city fire department. The system consists of small, break glass
circuit boxes located at various places in the building, and a master box
located in some convenient place. When a fire breaks out the alarm is
given by breaking the glass in any one of the alarm boxes. A plunger is
then released and closes the circuit connecting with the master box, thus

releasing a pre-wound mechanism and causing the sounding of the bells in

29.

all parts of the building. In case of a fire drill a key is inserted in
one of the alarm boxes which, of course, releases the plunger as above and
causes the alarm to sound. In both cases, after the alarm is sounded, it
is necessary to restore the master code box to its normal position by re-
winding it.

The Holtzer-Cabot Electric Company also manufactures several other
alarm devices. Among them are the following. The Non-interfering and the
Plain Code fire Alarm Street Boxes. Fire Alarm Transmitters for both types
of boxes. A silent test mechanism or attachment for fire alarm boxes to
meet the requirements of several states, which specify the necessity of
means for testing the box mechanism without sounding the gongs. Several
signaling devices, which consist of different types of bells and sounding
horns, are also a product of Holtzer-Cabot Electric Company.

A widely used fire alarm system of the present day is the Aero Auto-
matic fire alarm. This is a prOduct of the American District Telegraph
Company of New York City, hew York.

This system is a very sensitive system. The detecting element con-
sists of a small cepper tube less than one-twelfth of an inch in diameter.
This tubing is placed around the ceilings or roofs of the premises to be
protected. Air at ordinary atmospheric temperature is contained in the
tube and in the case of fire the air becomes heated and expands. At each
end or the tube there is a diaphragm or small metal box with real thin
sides capable of being bulged outward due to air pressure. On each side
of the diaphragm is an eleCtrical contact and when the air in the copper
tube is heated and caused to expand, the diaphragm becomes bulged and
completes an electric circuit. Connected in this electric circuit is a

transmitter which automatically sends the alarm to a central station and

50.

thus to the fire department. An annunciator placed on the outside of the
protected premises indicates the position of the fire. A general alarm
is sounded by bells throughout the premises. '

There are several other American District Telegraph Company Products
that are applicable to fire alarm control. Among them are the street
alarm boxes, the break glass type of box used in public schools and such
places, the automatic Sprinkler system similar to all other automatic
sprinkler systems, and several other alarm devices such as bells, sirens
and gongs.

The Globe Automatic Sprinkler Company of Philadelphia, Pennsylvania
is the producer of an automatic sprinkler system known as a Globe Saveall
Automatic Sprinkler. The Saveall Sprinkler is the first approved sprinkler
employing a solid chemical for its fusible element. This element has a
definite fusing temperature, and as the surrounding atmosphere attains the
temperature corresponding to the rating of the sprinkler, the chemical com-
pound undergoes a physical transformation changing from a solid to a liquid
and the sprinkler is in Operation. This sprinkler is adaptable for all
uses for it is manufactured in a wide range of temperature rating from 135°
to 540°. incorporated with this sprinkler system as with most others is
the automatic sounding of an alarm with the start of the fire. The detec-
tor for closing the electric circuit of the alarm is the water in the
sprinkler pipes. The water pressure acts upon a non-corrosive metal dia-
phragm. This Operates a knife switch causing an electric contact and
sounding an alarm.

The Globe Automatic Sprinkler Company also has on the market several

fire extinguishers. The most important of th se are the automatic type

51.

which are provided with a Saveall Detector unit similar to the one used

in the Saveall Automatic Sprinkler system. This Saveall detector causes
the extinguishers to be released. They are normally in an upright sus-
pended position and when released they are in the Operating position and
automatically begin to apply the chemical extinguisher to the fire. An-
other type of autOmatic extinguisher is held in upright suspended position
by means of a rope and fusible element. The heat of the fire releases the
rope by causing the fusible element to liquify, thus releasing the extin-
guisher into Operating position.

The Reichel System is an Automatic Fire Detection Service. It auto—
matically detects a fire at its start and instantly transmits a signal to
the Fire Department. This alarm system can be divided into the following
partsé the detector, the fire detector circuit, the contrOl unit, the
master transmitter of street fire alarm box, the local manual auxiliary
boxes, and the local alarm.

The Reichel detector is an electric thermopile. Sach detector con-
sists of seven couples in series, and each couple consists of one stud
of bismuth and another stud composed of some other metal. One end Of each
stud is imbedded in a porcelain base so that heated air won't come in di-
rect contact with it. The whole detector is mounted on the ceiling with
exposed ends down. As long as there is a difference of temperature between
the open end and the imbedded end, there will be a current flow. Since
the Open ends are extending downward from the ceiling in the case of a
fire they will become much warmer than the imbedded ends and enough current
will flow to Operate the alarm. A gradual rise in temperature will not
cause enough current to flow since the heat will be conducted away from

the Open ends fast enough to keep the difference Of temperature down.

32.

Each installation is divided into circuits. A circuit is composed
of a single wire with the detectors connected in series. A contact relay
is included in each circuit. The coil of the relay is so connected and
adjusted in the circuit that the supervising or normal current will hold
a pointer on the face of the relay in vertical position. In case there
is a fault in the circuit there won't be any current flowing and this will
be indicated by the relay needle moving to the extreme left. In case
there is a fire the needle moves to the right and makes a contact which
starts a fire alarm signal.

The contact relays mentioned above, are grouped in a hardwood cabinet,
with glass door through which the dials can be seen. Under each relay is
a printed designation of the area covered by the detectors on that parti-
cular circuit. This permits the cabinet to be used as an annunciator to
tell from whence the alarm originated. other relays and equipment essential
to the system are assembled in this cabinet and the whole is known as the
control unit.

the Master transmitter or street fire alarm box is located on the
outside of the building on the street. It is the same type as any regular,
city owned box. rhis is, of course, connected eleCtrically to the city
fire alarm wires so that Operation of this box will transmit a telegraph
coded number to the Tire department headquarters. rhe Easter Street Box
is automatically tripped from the control unit inside the premises. rhis
is possible by means of an electrically connected special auxiliary at-
tachment built in the master Street Box. When operated automatically this
attachment prOduces a mechanical motion equiValent to pulling the street
box. ihiS box can be used manually for any fire outside the premises the

same as any ordinary street box.

55.

rhe local manual auxiliary fire alarm boxes are located at the most
advantageous points, such as a preminent exit, elevator landing or some
such a place so that a local alarm can be >asily given.

One standard type horn or gong, regardless of the number of circuits,
is installed for a local alarm with each system. This alarm is located
on the outside of the building near the control unit so as to serve to di-
rect the firemen quickly to the control unit, and to act as a warning to
the occupants of the building that a fire exists on the premises.

In conclusion, it should be understood that there are several other
commercial alarm devices but that they all resemble, in a way, the appli-
ances that have been discussed. The main thing to be brought out in this

review of present types of commercial alarms is that there is not equip-

ment readily adaptable to a residential fire alarm system.

V‘.
Ij‘i'.

FIRE ALLRMS FOR HQSIUJHTIAL USE

In the selection of fire alarm equipment for residential use there

are several factors which must be considered.

1. Reliability over a long period of time without servicing.

2. Simplicity.

5. Low First Cost.

4. Low Operating Cost.

5. Appearance.

0. Quietness of Operation.

7. Mass of Installation.

The reliability or the sgstem is probably the most important feature
of a system. It is needless to say that if a system is not reliable it
fails to meet the need for which it is installed, namely, that of giving
a fire signal When it is imperative that it should do so. In large build-
ings, factories, etc., many systems are in use which are regularly ser-
viced by service men to maintain the reliability of the system, but could
this servicing be made unnecessary by the use of a system which is reliable
over a long periOd of time, much of the operating costs of a system could
be eliminated. This has, as yet, not been satisfactorily accomplished,
although much headway has been made in this direction during the past ten
years. This is, perhaps, one of the prime reasons why fire alarm systems
for residences has been, as yet, promoted unsuccessfully.

In a residence a diffexent situation exists from that of a factory
or large buildirs. A system designed for use in a residence must be one
which is reliable over a long period of time without servicing. The rea-
son for this is obvious. Although a system might be installed which re-

quires regular servicing, this regular servicing is almost impossible to

maintain. Any meter reader will admit that getting access to residences
is quite a problem. The lady of the house is quite frequently not at
home during the day, and if she is, it is undesirable to her to have a
service man taking the time necessary to service a set, especially if she
happens to be entertaining. Needless to say, there would be times when
the times between servicing of the system would be prolnnged, and in such
cases the reliability is, of course, seriously affected, hence the need
of reliability over a long periOd of time.

The simplicity of the system is rather closely allied with that of
first cost. It is also inherently a factor in the reliability of the sys-
tem, since simplicity of mechanism makes for better reliability to a cer-
tain extent. If the simplicity of mechanism of Operation can be brought
into an actual reality, the cost of manufacturing the equipment can be
greatly reduced, due not only to decreased amount of materials used, but
also to decreased labor necessary.

Low initial cost is vital if the system is to be made available to
the average man's residence. The prospective user of such equipment
thinks more in terms of first cost rather than in saving over a period of
time. Consequently, he is immediately prejudiced against such equipment
to-day, for most reliable equipment on the market now is expensive.

The fourth factor to be considered in selecting a fire alarm system
for residential use is that of operating costs. Although the average
American man might readily see the advantages of such a system, it is
doubtful whether he would use such a system if Operating costs were ex-
cessive. In times of stress, when curtailing eXpenses might become

imperative to him he is apt to class such a device as a luxury rather

56.

than the neCessity which it is, and to discontinue its use. Especially
is this true if the actual Operating costs amount to an appreciable amount
each month.

Little need be said concerning the appearance of the equipment. It
must be neat, and the thermostats, especially, must be designed for in-

conspicuous ness and harmony with the color scheme of the room.

C“

Quietness of Operation, while essentially unnecessary, is rather easily
achieved, and presents no very difficult problem.

Ease Of installation is a vital factor. It is preferable, of course,
to install such a system during the process of construction of the house,
but obviously this does not fit the majority of the situations. The resi-
dential fire alarm system must be such that it can be neatly and easily in-
stalled in any mOdern residence at a low cost.

In looking over the field of available equipment we found no equip-
ment which fully met all these requirements. Although each of the factors
inVOlved is more or less dependent on the others, and a compromise among
the various faCtors is necessary, our investigation of commercial equipment
available led to the fOllOwing discoveries.

l. That most equipment on the market to-day is designed for use in
large building, factories, etc.

2. That reliable equipment is expensive.

5. That reliable equipment is rather detailed equipment.

a. That most of the available equipment requires regular
servicing.

b. That most systems have, in our opinion, excessive
Operating costs.

0. That most equipment on the market is neat in appearance.

7. that most equipment on the market possesses quietness of

operation.

57.

8. That most equipment on the market is fairly easy to install.

Ur we might say, that such little equipment as exists which might be
auaptable to residential use has the disadvantages of requiring regular
servicing, high initial cost, and excessive Operating costs.

It is probable that the for going statements are eXplanetory of the
reason for lack of development in the use of resiuential fire alarm sys-

tems.

58.

LKPLdLiIHUlJIORK

Keeping in mind the essential factors necessary for a desirable resi-
dential fire alarm system, we have endeavore‘ to design equipment which
will fully meet these needs. The first problem which we considered was
that of suitable thermostats. Since the system must be reliable, and con-
forming with modern practiCe, have a pilot circuit which operates closed
(opening in case of trouble or fire and giving the alarm) the thermostat
must necessarily be one which opens the circuit when heated excessively.
Although we found a number of modern thermostats on the market which meet
requirements as to reliability, appearance, etc., all of them are rather
expensive. With a view toward a more economical design of a reliable and
neat appear'ng thermostat, we proceeded to design and construct two thermo-
stats. The first of these is shown on the next two pages both by picture
and mechanical drawing. The thermostatic element consists of bimetallic
brass and steel, secured from the Wilson Company, Newark, hew Jersey, and
built into the form of a solenoid. As the element suffers a change in
temperature the free end of the strip travels in approximately a circle,
tipping the mercury switch which is firmly mounted to it at that end. This
mercury switch (Con-Tac-Tor mercury Switch, Cat. ho. C 1028, Time-O-Stat
Controls Company) seems slightly larger than necessary, but has the most
sensitive action of any we were able to secure.

This thermostat is rather sensitive to temperature changes, and can
open or 01038 on decrements of temperature change of less than one degree

Centigrade at higher temperatures.

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41.

Below is listed the data taken on this thermostat at various operating
settings. In taking this data a temperature controlled box was used to
raise the temperature gradually to the tripping off point, and then gradu-
ally celled till it again closed the circuit, both temperatures being re—

corded.

Opening Temperature Closing Temperature
Degrees Cent. Degrees Cent.
90 88+
90 89
89.7 89-
90 89+
90 88+
100 98+
99 97+
100- 98
100+ 98.5
100 98
109.7 108+
110+ 108+
1lO 108+
110 108-
111 109+
121- 120-
120 119
120 119
120 119
120+ 119+
129 128+
129 128.5
129+ 128-
129.5 128-
129+ 128
159.7 159-
159.5 159
139+ 139
159+ 168.7

141 159+

In endeavoring to decrease the size of the previously discussed
thermostat, the following design was finally evolved. This thermostat,
shown on the fOllowing two pages by picture and mechanical drawing, has
a spiralled element. The same thermostatic bimetal is used in this ther-
mostat as was used in the one previously discussed. The mercury switch is
of the same type as that used in the case of the solenoid element thermo-
stat.

The part marked (adjusting screw) in the drawing is an adjusting
screw which determines the setting of the temperature at which the switch
will open. Although a neater and more compact thermostat was secured in
this later design, sensitivity was sacrificed as will be readily seen in
the following data taken in the same manner as was the data on the first
desifln.

The thermostat opens and closes the mercury switch on decrements of
temperature change of approximately 5 degrees centigrade. For the purpose
which this thermostat is to serve, however, this is of small consequence,
since we are primarily interested in a thermostat which will reliably Open
the circuit at a fixed temperature and give the alarm. This the thermostat
readily accomplishes. Further, we believe it can be favorably considered
from a standpoint of low cost, which was our chief objection to available
commercial thermostats.

The contacts of the thermostat are not liable to effects caused by

the elements, since they are inclosed.

 

 

 

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45.

,Data on Spiralled Element Thermostat

159

Opening Temperature Closing Temperature
Degrees Cent. Degrees Cent.
90.5 82
90+ 81
91.5 81.5
89.7 81
90+ 81+
98 91+
98.7 92
100- 92+
99.1 91.5
100+ 91.5
109.6 104
110.2 104+
109+ 104.2
109+ 105.9
110- 104.6
119- 115-
120.2 114.6
120.2 114+
121 115.2
120+ 115.6
128 125.5
128.5 125
150.2 125+
129.6 124.5
129.6 125
141 154.7
141 155.6
140+ 154+
141 155-

155+

 

45.

With this final design we left the question of thermostats to turn
our attention to the problem of a suitable relay. The problem which con-
fronted us here was that of designing a relay which would conform to the
following requirements.

1. Close the secondary contacts upon failure of the exciting
voltage.

2. Low initial cost.

5. Low Operating cost.

4. Contacts which are not affected by the elements or ageing.

Most of the commercial relays investigated were found to be:
1. Rather expensive, if reliable.
2. Many were designed with secondary contacts exposed to air.
3. High initial cost of equipment giving reasonable operating
costs.

4. High operating cost of equipment having a reasonable initial

The problem was by no means a simple one. Three designs were worked
out and the relays constructed. These failed utterly to meet our speci-
fications. All of these designs were then altered with little success,
and finally abandoned as useless for the purpose.

After considerable effort and profitable experience, a design meet-
ing the requirements, as we see them, was finally evolved. It is shown

on the two following pages by picture and mechanical drawing.

47.

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e9.

The exciting coil consists of 600 turns of number 50 cotton covered
copper wire. The armature consists of a permalloy strip, possessing very
high permeability, which was supplied to us by the'Weston Electrical In-
strument Company upon request. This strip, of dimensions .0001 x 1/16
x 4 inches, lies flat along the tube, the free end dipping into mercury
and forming a closed circuit through the tube when the exciting coil is
inactive. When the coil is excited the strip is attracted vertically up-
ward, and floats with the tip free of the mercury. The length of stroke
can be adjusted either by raising or lowering the tube with a given ex-
citing current, or by varying the exciting current. The first method is,
of course, the more proactical since a change of exciting voltage can not
be readily had in most cases.

In running tests upon this relay (data listed on next page) we found
that the relay would operate successfully on voltages from 2.8 to 7.1
volts. At 2.8 vOlts the stroke becomes a minimum and at lower voltages
the strip fails to pick up. At 7.1 volts the stroke has its maximum valye
without making contact with the upper part of the glass tube. At higher
voltages contact with the glass occurs, and the relay becomes slightly
noisy.

We found the best Operating voltage to be about 5 volts, the stroke
adjusted at this voltage to approximately l/lb”. At this voltage the
coil takes a current of .15 amperes, and has a power consumption of .575
watts. Operating under these conditions the yearly operating cost would
be (assuming 5 cents per K. W. Hr.) 16+ cents.

Another feature of this relay is its quick action. Of all of the
commercial relays tested we found none which had quick enough action to

open the secondary contacts before ringing of the bell took place, as in

50.

cases of resumption of power source after failure. This relay operates
quickly enough to Open the bell circuit before ringing Of the bell can

take place in such instances.

exciting werm. Power Calc.
Current Volts Consumption P.F.
(Amps) (Watts) (%
.08 2.8 .125 57.9 — pickup voltage.
.120 4.1 .250 50.9
.150 5.1 .575 49.02 - Best Operating
Conditions
.180 5.0 .560 52.4
.210 7.1 .750 50.5

Current Capacity of Primary: Does not show excessive heating at 1.5 amps.
Current Capacity Of Secondary: Five Amperes - Ample capacity for any
residential bell.
We believe that this design fully meets the requirements for resi-
dential fire alarm use, although further work toward a more compact de-

sign Of this same type relay is desirable.

 

U‘)
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0

Conclusions

in making this investigation Of residential fire protective equip-
ment, as portrayed in the foregoing pages, we have arrived at several
very definite conclusions. The problem which presented itself is by no
means a simple one, and while we feel that we have made a very substan-
.tial progress in the right direction, during the time allotted to this
work, we are convinced that a worthy field for study still exists in this
subject, for we have by no means arrived at the final solution of the prob-
lem. For this reason we shall endeavor to set forth here the work which
we believe necessary to bring this problem to its final solution.

fibers are three factors, aforementioned, which must be kept firmly
in mind. First, reliability or certainty of Operation over long periods
of time-without servicing. Second, simplicity or low initial cost. whird,
low Operating costs.

We believe that the relay designed and constructed by us embodies the
first and third requirements in full, and believe that it can be modified
to meet the second requirement in full. It should be possible to construct
the magnetic arrangement using a single or double pOle core, and to shorten
the length of the tube without seriously affecting either the reliability
or the Operating costs. If this can be done, the design can be made much
more compact, and will contain less actual material, with a consequent low:
ering of first cost. It might also be feasible to construct a relay along
these lines which will Operate directly from 110 volts, 60 cycles, thereby
eliminating the use of a transformer. The cost Of a suitable transformer

might well offset the added cost Of such a relay, however.

 

05.

Another phase of the subject which time did not permit us to study
was that of suitable bells for such a system, and in furthering this in-

vestigation we would recommend that this be studied.

***********#

BIBLIOGRAPHY

1. Annals of the American Academy of Political Science - Fire Prevention

September 1905

Scientific American

Novelties in Fire Alarm - Scotch and Danish Inventions
V - 92, Page 519. April, 22, 1905
Automatic Chemical Fire Extinguisher
v - 87, Page 174. September 15, 1902
Guarini's Wireless Fire Alarm Apparatus
V - 89, Page lee. September 5, 1905
A Fire Detector by Charles H. Kayser
V - 115, Page 578. December 25, 1916
Using Telephone Lines for an Automatic Fire Alarm System
V - 115, Page 127. August 5, 1916
An Automatic Fire Alarm - 00mpressed air Type-
V - 108, Page 180. February 22, 1915
A Fire Alarm System Which Telephones its Message
'V - 122, Page 494. May 1, 1920
An Improved Box for the New York Fire Alarm Telegraph
V - 110, Page 251. March 14, 1914
Wireless Telegraphy in New York Fire Department
V - 110, Page 25. January 3, 1914
A Fire Alarm System for New York
V - 100, Page 458. dune 12, 1909
German Fire Alarm System

V - 71, Page 148-149. May 11, 1911

5. Scientific American Supplement
The Siemflns and halske Fire Alarm
V - 56, Page 251. September 19, 1905
Gong Arrangement for Fire Alarm
V - 6b, Page 148.’ September 5, 1908
Thermoscope
V - 76, Page 597. December 20, 1915
The new York Fire Alarm System
V - 78, Page 548. November 28, 1914
4. American City
A Compress-Air Fire Alarm Signalling System
v - 25, Page 351. October 1921.
Fort Worth's New Fire Headquarters and Fire-Alarm Control Office.
V - 45, Page 85. July 1951
Nashville, Tennessee Fire Department
V - ea, Page 156—157. April 1951

”ham Alabama

1, 1

A Complete Modern Fire Alarm System, Birmin

V - 26, Page 455-a5e. May 1922
5. Bulletins

howe Signa1 Company, Chicago, Ill.
Protective Signalling Systems - 1952 Copyright

The Gamewell Company, newton, Massachusetts
1929 Model Dualarm - Cat. L. 2002, 4-7-29
Rockwood Sprink—La-Stat - Photo 4659-1
New Gamewell Three—Fold System - Bulletin 1505, 1in-11-29

Gamewell Diaphone - Cat., L. 2072, 5M-2-5l

 

Holtzer-Cabot Electric 00., Boston, Massachusetts
Fire Alarm Systems For Schools - Booklet No. 18504 A
American Dist. Telegraph Co., Dew York, New York
Supervisory Service For Sprinkler Systems, Bulletin Form 904 A
Night Watchman. Supervision and Hanual Fire Alarm Service
Bulletin Farm 902 B
Aero Automatic Fire Alarm - Bulletin Form 950
Globe Automatic Sprinkler 00., Phil., Penna.
Globe Automatic Sprinklers
Globe Saveall Sprinkler
Globe Fire Protection Equipment
Fire Detection Service Department of Pacific Fire Extinguisher 00.,
San Francisco, California
Semidrechnical Description of Fire Detection Service (Reichel
System) 1925, Copyright
National Fire Protection Association, Boston, Mass.
Facts About Fire - 12M-8-52
Boston Insurance Co., Lansing, Michigan Division
Annual Property Loss Due to Fire for the last 57 years

1875-1951 inclusive

$3139???“
HUME-‘1 U95 (M 1
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