ALARM SYSTEMS AND ACCESSORIES
History Shows Progress Toward Certainty of Operation and an Increasing Development to Meet Modern Requirements—The Siren Fire Alarm Popular Compressed Air Systems
THE history of fire alarm telegraphy shows progress toward certainty of operation and an increasing use of alarm apparatus to meet modern requirements. The first fire alarm telegraph system in the United States was installed in Boston in 1852. It was a crude design of single circuit type. At the present date fire alarm telegraph systems range from single-circuit systems adequate for small towns to systems of many circuits, requiring forces of operators constantly on duty in the central stations. They may be classified under two general headings, namely, automatic and manual. Theword “automatic” may only be applied to systems which require no manual intervention whatever in transmitting alarms from the street signal boxes to the fire department. When a system becomes large enough to warrant the constant attendance of one or more operators at the central station, it ceases to be entirely automatic in its functions and requires facilities for the manual transmission of signals from the central station to the fire stations.
The following table, taken from a report issued by the Bureau of the Census in 1915 on municipal signalling systems, gives an idea of the great growth in the use of fire alarm telegraph apparatus.
During the decade ending with 1912 there was a rapid development of the fire alarm signaling systems of the cities. The miles of wire used for the service increased from 54,710 in 1902 to 90,284 in 1912, a net gain of 35,574 miles, or 65 per cent. During the same period the number of boxes increased from 46,767 to 81,282, or 73.8 per cent. The rate of increase from 1912 up to the present year has been slightly less than for the preceding decade, due principally to conditions incidental to the war.
One of the improvements that have characterized the installation of signalling systems during recent years has been the placing of wire in subways or conduits. This tendency is in harmony with the practice of removing electric wires for lighting, power, telephone, and telegraph service entirely from overhead construction and placing them underground. Underground service is especially desirable in the cases of fire alarm systems whose successful operation in all conditions of weather is of prime importance. A tabulation recently compiled, covering 132 cities of 30,000 population or over, showed a total of 45,595 miles of wire underground. Nearly all of the underground wire is located in the larger cities, it being estimated that less than 1,500 miles of wire were placed below street surface in all cities under 30,000 population. The following cities, included in the above tabulation. reported, in the order named, the greatest amounts of fire: Detroit, Washington, Chicago, New York, Cleveland. Milwaukee, and Boston. The underground wire reported for these cities formed 54.6 per cent, of the total for all cities.
There is no reason to believe that the rate of growth in the use of fire alarm telegraph apparatus will fall below that for the period described above, but on the contrary conditions point to unprecedented period of activity in this branch of fire protection.
During the past few years a great change has taken place in the type of alarm equipment employed by towns and villages. The presence of electric power throughout the entire country as well as the development of the motor driven fire alarm siren has resulted in the widespread adoption of this device for fire alarm signalling in towns and villages. Its simplicity of operation and negligible upkeep cost, as well as its peculiarly penetrating sound, makes it particularly suitable for this service. Its adaptability for remote control is another factor in its favor. There is still room for improvement in the electric siren fire alarm, for with the present design it is quite difficult to transmit the location of fires by code thereon, due to the time required for the rotor in the siren to slow up and produce a break between signals. It is likely that this fault will be soon overcome to make the siren a still more satisfactory alarm apparatus for the rapidly increasing number of users.
An effort was made recently to produce an alarm system for volunteer fire departments that operated in connection with telephone system, the arrangement being such that each member of the department having a ’phone in his residence or office would be notified thereby of the presence and location of a fire. The development of the electric siren about the same time with its many advantages reduced the demand for the former type of apparatus, and at present little is heard of it. The future of the telephone alarm system, w hich is of greater initial cost, as well as cost of upkeep, is uncertain.
Steam whistles will be used for alarm purposes as long as there are steam power plants available and officials therein sufficiently obliging to co-operate with the fire department in sounding the signals communicated to them. The steam whistle has a greater carrying range than the electric siren but this is offset by the necessity of maintaining steam pressure for its operation. Industrial plants which have their own fire brigades and maintain steam pressure probably find little advantage in using any but the steam signal, outside of remote control feature of the electric siren. The steam whistle has one distinct advantage over the latter, namely, its ability to give short sharp blasts in sounding out any particular box location.
Compressed air fire alarm apparatus possesses practically all the features of the steam whistle, and in addition its does not require maintaining steam pressure. Air pressure is kept up by electric driven compressors and which are self regulated. However, it requires compressors of quite large proportions to provide sufficient air for sounding long signals.