REMOTE INDICATOR SYSTEM FOR E21 SERIES AUTOMATIC G-AGENT ALARM
I. M. Derr · Defense Technical Information Center (DTIC) · 1965
A remote indicating system was developed for incorporation into the Navy's E21 Series Automatic G-Agent Alarm installations so that a number of remote E21 gas-attack alarm units could be monitored at a central control. An alarm sounds at the receiving station when gas is sensed, and a red light indicates the location of the E21 unit that has sensed the gas. As a precaution, a warning indicates the presence of a signal on the assigned radio frequency that may cause either intentional or unintentional jamming of the frequency. The Remote Indicator System consists chiefly of (1) a transistorized frequency- modulated transmitter mounted in the E21 gas alarm, (2) a transmitting antenna mounted on the gas alarm case, (3) a tone generator producing a modulating tone in the frequency range of 800 to 3600 cps, (4) a programmer to allow time sharing of the frequency by several transmitters, (5) a receiving antenna, (6) a receiving station consisting of one FM radio receiver, 15 Motorola single-tone decoders, one signal presence indicator, and associated power supplies. The system was successfully field-tested at a variety of transmitter-to-receiver distances. The maximum distances tested were 4.7 miles over obstructed terrain and 9.8 miles over unobstructed. The transmitter actuated the central alarm in all cases.