. Scientific American Volume 78 Number 01 (January 1898) . is the logical development of the usage of thethermostat above referred to. In place of a set of wiresconnecting a number of isolated thermostats, the wholewire itself is so sensitive that the mere heat of a lightedmatch (see Fig. 3) applied at any point of the wire willcause the metal to fuse and ring in an alarm. As thevalue of a fire alarm consists chiefly in the rapidity withwhich it will act, upon the outbreak of a fire, it is evi-dent that the efficiency of the fire cable is enor-mously increased over that of ordinary systems. Th
. Scientific American Volume 78 Number 01 (January 1898) . is the logical development of the usage of thethermostat above referred to. In place of a set of wiresconnecting a number of isolated thermostats, the wholewire itself is so sensitive that the mere heat of a lightedmatch (see Fig. 3) applied at any point of the wire willcause the metal to fuse and ring in an alarm. As thevalue of a fire alarm consists chiefly in the rapidity withwhich it will act, upon the outbreak of a fire, it is evi-dent that the efficiency of the fire cable is enor-mously increased over that of ordinary systems. The construction of the cable and the details of thewiring are shown in the accompanying figures. Thecable. Fig. 1, is made up of an inner copper wire,which is coated with a metal that fuses at the lowtemperature of 374 degrees. The fusible metal alonewould serve to carry the current, but the copper is in-troduced to increase the conductivity. Around thefusible metal is wrapped a suitable insulation, andover this again is wrapped a series of smaller wires. 1. The cable. 2. Cron eecUon of cable. 3. Fualng cable with a lighted match. 4. Cable in pipe for nae on central lire atation. 6. Wiring of room and alarm connnctiona. DETAILS OF HVLTIFHASE CABLE FIBE ALABH. with insulations between them, as shown in the sketch,the whole being covered with au outer protective wrap-ping. One of the outer wires serves the fire alarm,another the burglar alarm, another may be used forthe servants call, and others may be added to servea multiplicity of electricconnections. When a fire breaksout in the neighbor-hood of the wire, theheat fuses and expandsthe inner fusible coat-ing and forces it outthrough the insulationinto contact with theoverlying return wire,thus forming a metalliccontact between theinner and outer wire,closing the circuit andturning in an 6 shows the cablelaid in a room and con-necting with an audiblelire alarm in the house. Fig. 5 is a diagram show-ing the c
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