METHOD FOR CENTRAL SIGNALLING TO INDICATE CONDITION OF OBJECT Russian patent published in 1994 - IPC

FIELD: central signalling methods. SUBSTANCE: in case of an emergency situation in guarded object, the operator stationed therein activates a low-power transmitter which, in turn, switches on the main transmitter concealed in the guarded object. Coded alarm signal starts to be repeatedly sent to central station. After repeated exchanges between relay station and central station and after comparing the received pulses, a signal is generated which switches on a call indicator concealed in the door of the guarded object. The preferable duration of alarm signal pulses is 1-2 s at a cyclic recurrence of pulses of 50-100 and a pulse duration of (0,2-0,4)·10^-3s. On arrival at the object the emergency squad check the correctness of the address by the readings of the call indicator and, on completion of the control operation, remove the signal from the call indicator by an appropriate code. EFFECT: higher efficiency. 3 cl