Fire Alarm Systems for Small Towns

Fire Alarm Systems for Small Towns

Necessity of Complete Systems for Small Villages—Efficiency of the Telegraph Alarm—Telephone a Poor Substitute for It—Single Unit System—Compressed Air System


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Systems for Small Towns

Most of the devices thus far described have as their sole purpose the object of making known the existence of a fire and it is rather singular that scores of small communities that have been willing to raise ample appropriations for the installation of effective water distribution systems and have purchased modern motor driven fire apparatus, have apparently not considered it good policy to pay for an equally modern fire alarm system. Neither an ample supply of water at good pressure nor an efficient fire department can render the maximum protection to a community until the means are at hand not merely for letting the department know that there is a fire but where that particular fire is. One of the chief reasons for the staggering total of American fire losses every year is to be found in the fact that so many of our fires are allowed to get well under way before the department reaches the scene. Undoubtedly we are more careless than people on the other side and we have a far greater amount of flimsy and inflammable construction than is prevalent in older countries, but the records of large cities like New York and Chicago show what a very small proportion fires causing serious loss bear to the total number in a year. This is largely because nine out of ten fires are extinguished before they can gain any headway where an effective alarm system is in use. The first few minutes are always the most important in fighting any fire.

At the present writing about five hundred communities in the United States, having a population of one to five thousand, have installed fire alarm signal systems and the usual experience has been that the installation paid for itself in a comparatively short time. Doubtless the reluctance of a greater number to do likewise may be accounted for, in some measure, by the universal spread of the telephone and the reliance that is placed upon it. But that the telephone is a poor substitute for an automatic signal system may be realized when the difference in time required to transmit a signal is considered. In a recent fire in New York City where the telephone was relied upon as an alarm, nine minutes were wasted in getting in touch with the department before an alarm was sent in from the nearest street box and several people lost their lives in consequence. No one appreciates the value of the first few minutes in effective fire fighting more than the fire underwriters and they do not recognize the telephone as a substitute for a signal system. In many States, the difference in the insurance rates granted where there is a signal system is more than sufficient to pay for the cost of maintenance and the interest on the investment in a modern installation.

Types of Signal Systems

Even the simplest form of fire alarm telegraph system conforms in its general principles to those used in the largest cities and is equally complete and reliable, the difference being chiefly that of size. It consists of a number of alarm boxes, such as that shown in Fig. 7, located on poles or the outside of buildings and accessible to the public. In the engine house and at the waterworks and power station, there are indicators, or registers, to record the numbers of the box stations and gongs which sound the numbers, each alarm box having a number which indicates its location. The operation of a signal box merely consists of opening the door and pulling down the hook. This sounds the box signal number four times in succession on all of the gongs in the system simultaneously, regardless of where they may be located, and will also sound a public alarm at the same time. Everyone in any way concerned with the fighting of a fire is notified at once, the engine company, the waterworks, town officials, and the public generally, and the location of the fire is also made known. For the public alarm, the most satisfactory and reliable method is the use of a bell or whistle located on a high tower. The whistle may be operated by compressed air, an electric motor constantly maintaining the desired pressure in a tank automatically as in railway air brake systems, so that no attendance is required.

Fig. 7—Standard Fire Alarm BoxFig. 11—Plant of Compressed Air System as Used at Pelham Bay Training Station

In addition to the locations already mentioned, it is customary in many places having a fire alarm telegraph system to install boxes at schools, hospitals, theatres and factories. Where installed on private premises, they are usually paid for by the owners and are thereafter maintained as a part of the public system. These boxes sound the alarm numbers in the same manner as those installed at the engine house and waterworks, indicating the location of the fire. The fire alarm system can also be used for incidental purposes such as transmitting the correct time at noon or other hours, the opening and closing of school service and for police or ambulance calls in special emergencies.

Single Unit Systems

For communities that do not wish to go to the expense of a fire alarm telegraph system such as that described above, there are two types of systems designed to give the location of the fire in a general public alarm. The latest of these to be placed on the market is known as the “King Unit Type Bell Striker” and is illustrated in Figs. 8 and 9, the former showing the bell striking mechanism and the latter the transmitting device. The latter may be located in the fire chief’s house, the telephone exchange, railroad station or other central location where an attendant is constantly on duty. The mechanism of the transmitter is similar in principle to that of a fire alarm telegraph box, but owing to the necessity of transmitting all signals from one device, it is not automatic. There are twenty numbered wheels placed on spindles mounted on a slate base. When an alarm is received, the attendant selects the wheel corresponding to the location of the fire, places it on the wheel holder in the transmitting box and pulls the lever.

This causes the bell striking mechanism to sound an alarm giving the number selected. The alarm may be sounded at a maximum speed of one stroke of the bell per second and may be repeated as often as desired. The complete bell striking mechanism, which is of the electromechanical type, is housed in a weatherproof cast iron box and needs no attention other than occasional winding. With the weight raised to the position shown in the illustration, it has a capacity of thirty-six hundred blows. This bell signal may also be used as an auxiliary in connection with a telegraph system, in which case it is connected with the various street boxes and is sounded automatically from them, the transmitter shown then being dispensed with. The bell striker and transmitter constitute one of the simplest types of location signals and has the advantages of being easy to install and inexpensive to maintain.

Compressed Air System

Where the community spreads over a territory that cannot be reached effectively by a bell and it is desired to use a public alarm in connection with a street box signal system, a compressed air system has been specially designed for this and has been adopted in quite a number of communities. This compressed air signal system consists of a Gamewell Diaphone, or special type of horn, a compressed air reservoir nine feet long and three feet in diameter, a special Smith valve which operates when the street box is pulled, and the necessary gauges and piping. The Diaphone, Fig. 10, is of the same design as the horn used for fog signals on the lightships and lighthouses of the Atlantic and Pacific Coasts, the Great Lakes and along the St. Lawrence River. Under favorable conditions these horns have been audible at a distance of ten miles on land, while one installation in a hilly country has been heard six to seven miles.

This system should not be confused with the older steam whistle systems mentioned earlier in the present article and which required a cumbersome whistle blowing machine to operate them. The latter has been replaced by the Smith electric valve, to which reference has been made above. This valve requires no winding or any other source of power except that used in the main line of the signal system, i. e., the electric current. The clockwork of the whistle blowing machine is accordingly dispensed with, which materially decreases the cost of installation, while the absence of moving contact points in the valve itself makes it reliable over extended periods without attention.

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Fig. 8—King Unit Bell Striking MechanismFig. 10—Diaphone Horn of Compressed Air SystemFig. 9—Transmitter of King Unit System

Fire Alarms for Small Towns

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A complete installation of the compressed air type is illustrated by Fig. 11. This shows the compressed air reservoir and the air compressors direct connected to electric motors, the compressor units being provided in duplicate for emergencies. The operation of this part of the plant is automatic since it is provided with controlling devices set to maintain the air in the reservoir at the desired pressure. When desired these systems may be operater by the Gamewell standard whistle blowing machine, the same controlling devices being employed to maintain the pressure. The use of the Diaphone in connection with these systems produces a distinctive note of unusual carrying capacity with an economical consumption of compressed air which accounts for the use of but one storage reservoir instead of two or three as was previously necessary. In addition to having been adopted by a number of communities of five to ten thousand popution, compressed air systems were adopted during the war in some of the cantonments and naval stations.

Fire Alarm Systems for Small Towns

Fire Alarm Systems for Small Towns

The Siren a Favorite Signal in General Use—Description of Different Types Made—Solenoid Brake Attachment for Transmitting Numbers and Varied Note Signals



HISTORY doesn’t tell us how many alarms were sounded when Babylon was reduced to ashes nor what kind of a system the Romans had in use when Nero touched the city off in order that he might fiddle by the light of a big bonfire, but in the centuries that elapsed between that time and the middle of the nineteenth nothing more elaborate than some means of making a noise had been devised. There was naturally not much use for an alarm of any kind before volunteer fire departments came into existence, though undoubtedly the occurrence of a fire was signalled by beating a drum, blowing a horn or ringing the church bell even when there was no organized means of fighting it. If railroads had been common in those days and the town were located at a division end, probably it would have had a discarded locomotive tire and a second-hand sledge for its complete alarm system, as so many American towns and villages have in the past half century. When there was no wind or it happened to be in the right direction, such an alarm can be heard a fair distance but it represented about the most rudimentary device possible and its sole advantage was that of cheapness.

The Bell a General Standard

The first step in advance over the home made device just described is the fire bell mounted in a special tower and designed to be operated by hand. This is an outgrowth of the use of bells in church towers and for many years such an installation constituted the entire alarm system of even good-sized towns. Even to-day it is probably in use in a far greater number of communities than any other form of alarm and its adoption for this purpose continues to progress. Where a bell of sufficient size is selected and it is mounted well above the average height of the surrounding buildings, it is plainly audible for long distances except under adverse weather conditions. The latter is true of any audible signal to some extent, since a strong wind will always nullify its effect somewhat in that part of the community that happens to lie to leeward of the tower at the time the alarm is sounded. It is likewise true that use of the bell or any other form of signal designed to be generally audible when sounded from a central location, is limited by the size of the community. The distance at which it must be heard to be effective is not only a limitation but the time required to inform the attendant at the tower from an outlying district also works against it, though the general use of the telephone in recent years has done much to offset this.

Whistles and Sirens

As communities grew and expanded, the bell type of alarm was most frequently replaced in earlier days by a steam whistle, usually installed at fire headquarters. While manually operated in many instances, these whistles were sounded to give code numbers indicating the location of the fire by wards or districts and were in fairly general use in cities up to one hundred thousand about twenty-five years ago. They had many disadvantages, not the least of which was the requirement of constantly keeping up steam pressure. Where the latter was not available at its maximum at the time of sounding an alarm, the latter was far from being as effective as might be desired in such an emergency.

For scattered communities, villages and moderate sized towns, the electrically driven siren has almost completely displaced the old-time steam whistle and to a large extent, the manually operated bell. Its distinctive and piercing note not only has the advantage of being audible to a much greater distance even under adverse conditions of wind, but it can be operated from any one of a number of distant points merely by the closing of a switch. As in the majority of very small communities, no one is stationed constantly at fire headquarters, this considerably shortens the time necessary to turn in an alarm.

Fig. 1—Double Head Electric SirenFig. 2—Automatic Control for Electric Siren

Types of Sirens

The modern siren must not be confused with its predecessor designed to be operated by steam and which was in fact, merely a special type of steam whistle capable of producing a sound ranging over an octave or more. One of the chief advantages of the present day type of siren is that it requires no steam pressure. Being driven by an electric motor, it is always ready for service. The sound is produced by the rapid rotation of a series of vanes or blades in the form of a wheel, in close proximity to a series of openings in a stationary member. The former is termed the rotor and, as will be noted in the illustration, Fig. 1, (Denver siren) it revolves inside the stationary member, termed the stator. The latter is of cast iron and is bolted directly to the base of the same material. The rotor is of aluminum and very carefully balanced so that it can be run at high speeds. It is mounted directly on the shaft driven by the electric motor through a flexible coupling which is provided to guard against any sight inaccuracy of alignment since the rotor must run very close to the stator to be efficient. To effect this, both the stator and the rotor are accurately machined and lined up true in order that the latter may run as close as possible to the former without actually touching.

The siren shown in the illustration is of the quadruplex type consisting of two duplex units and is driven by a five horsepower G. E. three-phase 110-volt motor (alternating current). The manufacturers recommend that, wherever possible, this type of motor be used, as it is simpler and more satisfactory than either a single phase, alternating current motor, or a direct current motor. The pitch of the sound produced by this siren at full speed is that of high C, or two octaves above the middle C of the piano, and it provides the most effective alarm by allowing the motor to reach full speed and then opening the switch for five seconds and closing it again. In this way, the sound not only carries further but takes on the characteristics of an alarm and cannot be confused with any other. The quadruplex siren is designed for communities up to 10,000 population; the duplex, or single unit type which is run by a three horsepower motor, being used for smaller towns and villages.

Varied Note and Number Signals

Mention has been made above of the fact that the characteristic rising and falling note of the siren is produced by varying its speed by opening the motor circuit at intervals and holding it open for a given number of seconds. The same effect is produced automatically by the installation of a flasher in the motor circuit. This device, shown in Fig. 2, is commonly used in connection with electric signs or illuminated displays in which various parts of the design or wording is flashed on and off in a given sequence. It consists of a shaft carrying electrical contacts, their size and number being determined by the purpose for which the flasher is designed. Brushes bear on these contacts and as the shaft is rotated by a small electric motor, these brushes alternately open and close the circuits. The flasher illustrated is made especially for use with this siren and is designed to be placed near it when in service. From the flasher, circuits are run to as many points, whether local or distant, from which it is desired to operate the siren, ordinary five ampere snap switches being used on these circuits. When one of these control switches is closed, the main switch automatically closes for 10 seconds, opens for four seconds, closes for two seconds, opens for four seconds and so on in a regular sequence, until the control switch is again opened. A slightly different form of this device is sometimes used in which the operation is the same with the exception that, after operating for two minutes, the device automatically cuts itself and the siren out of the circuit, but remains in position to start up again as soon as the control button is pushed again. With this automatic type, a momentary contact switch is used for the control.

As described above, the siren is designed simply to give a general alarm, which is usually considered all that is necessary for village and small town use. Where it is desired to transmit number signals, the solenoid brake attachment, shown in Fig. 3, is used. This brake is electrically operated and instantly releases when the control switch is operated, permitting the siren to run at full speed, but the moment the switch is opened, the spring applies a heavy pressure on the brake bands and clamps them against the brake drum, bringing the siren to a stop in about ten seconds, so that number signals or any desired code may be sounded rapidly. A more elaborate type of control is provided by a device, two types of which are made, the simpler producing two different alarms, one for fire and the other for police help. Any number of control stations may be established and at each two push buttons are installed, one red and the other green. When the red button is pushed, the fire signal sounds, ten seconds on, four seconds off, four seconds on, two off, ten on, four off, four on, two off, and repeat until reset. The green button gives the police signal which is ten on and four off, repeating until reset. Through the use of the other type, selective signals may be sounded, but for this purpose special fire alarm boxes which will transmit over the lines a predetermined number at the correct speed, are required.

Fig. 3—Brake Attachment for Bringing Siren to Rest QuicklyFig. 5—The Outgrowth of the Auto Siren Introduced Sixteen Years Ago

The siren shown in Figs. 4 and 5 (Sterling) is a pioneer in this field in that it was first introduced sixteen years ago for automobile use. At first it was considered entirely too loud for that purpose, the ordinary bulb horn then being generally employed. In the’course of a few years, however, the adoption of the motor fire truck made a distinctive and powerful signal necessary and the hand-operated siren came into use for that purpose. It is still employed on many pieces of motor fire apparatus throughout the country and particularly the insurance patrol cars in many of the large cities. The extensive use of these small sirens led to their development as a general fire signal in the power driven form illustrated. In this type, the motor is placed between the units where a double head is employed. The base on which the motor is mounted also carries an adjustable support which holds each siren head in perfect alignment. Inside the housing to which it is machined to a close fit is the aluminum rotor, securely keyed to the motor shaft. The turning of this rotor and the cutting off of the air by its vanes at the ports or openings of the housing produces the siren note. Although the aluminum rotor is very light, the motor bearing is not depended upon to carry its weight, a large end bearing being provided in the housing to support the end of the motor shaft. The illustration also shows the solenoid, or magnetic, brake which immediately brings the rotor to a stop when the circuit is opened. As previously described a siren thus fitted is employed for transmitting number or code signals and quite a number of them were supplied during the war for this purpose.

A clearer idea of the manner in which a siren operates may be had from the phantom view of another type, Fig. 6 (Federal). In its revolution at a high rate of speed, the rotor draws air in through the large bell-mouthed openings, or horns, at either end, and drives it out through the ports in the stationary housing, the alternate opening and closing of these ports by the turning of the rotor producing the characteristic note of the siren, while the rising and falling sound which makes it so distinctive is the result of a change in the speed of the motor. The latter is brought about by opening and closing the switch by hand, or by means of the automatic control apparatus previously described. The sheet steel hood placed over the upper ports of the stationary housing serves as protection to the siren by keeping snow and sleet out of it in winter and rain in summer. Both of the types of sirens just described are built as single as well as double units, although only the latter is illustrated. They are also adapted for operation by means of the automatic control apparatus designed for transmitting number or code signals, as previously explained.

(To be continued)

Fig. 6—Phantom View of Electric Siren