Fire Alarm
Collier's New Encyclopedia (1921)
elective signaling central office for the purpose of notifying the fire department in case of fire. The instrument is usually reduced to its simplest dimensions so that people not familiar with the system may operate it. Fire-alarm boxes contain devices to make and break electric currents. There is usually a wheel provided with teeth separated by a non-conducting substance and this when turned comes in contact with a spring which opens and closes the circuit at each tooth, thus producing a signal at the central station. The number of the signal box is usually indicated by the arrangements of teeth and spaces and in that way the fire is located. Access to the crank or chain by which the signal is communicated is obtained either by a key or by twisting the door handle or by breaking the glassthis last being the method most in vogue in large cities. Telegraph instruments connecting with headquarters for the use of firemen are often attached. The signal may be registered on a Morse recording ing instrument or by some similar device. In some districts there is an apparatus by which the signal results in the ringing of tower bells or the sounding of steam-whistles. The last method, now supplemented by electricity, was formerly in general use, but the development of the electric telegraph has resulted in greater speed and in many simplifications. From the middle of the 19th century telegraph boxes have been in use in Boston, and improvements such as the non-interfering pull and successive feature have brought the fire-alarm system to its present perfection. FIREARMS. See AMMUNITION; AR- ORDNANCE; Etc.
What Has Changed in the Last Century
The Collier's account of 1921 describes the street-corner telegraph box, with its toothed code wheel tapping out the box's number to a central station, as having reached "its present perfection." That network has largely vanished: the telephone did most of the work by mid-century, the first US 911 call was placed in 1968, and today the overwhelming majority of fire reports come from mobile phones, with cities such as Chicago removing their alarm boxes outright (New York and Boston have kept some as a backup). The bigger change is that alarms moved indoors -- cheap battery smoke detectors spread through American homes in the 1970s after building codes began requiring them, and automatic sprinklers and monitored building systems now call the fire department without any human pulling a lever.
Written for this edition, 2026.