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
(Continued from page 881)
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.
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.
(Continued on page 937)
Fire Alarms for Small Towns
(Continued from page 931)
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.