Audio burglar detection system for bank - has microphone in protected area receiving coded audio control signal and initiating alarm if any variation is detected

摘要

The sound system monitors a protected area to detect an intruder, providing an alarm even when the surveillance microphone is blocked. The surveillance sound system has a connection circuit linking a transmission line to a surveillance line, a microphone being connected to the surveillance line. An audible transmitter is fed from a generator so as to produce a coded audible control signal. This signal is received by the microphone, to verify the orrect operation of the surveillance system. If a signal other than the correct coded signal is received by the microphone, because of additional noise, or suppression of the code signal, then an alarm signal is produced.