LOCAL EMERGENCY COMMUNICATION SYSTEM Russian patent published in 1998 - IPC

FIELD: radio engineering; transmission of short messages. SUBSTANCE: system has at least one transmitter that radiates radio signal frequency-keyed by data signal; keying rate of each transmitter is chosen from condition R = (1-5)P/h²N_o, where h² is actually desired signal-to-noise ratio at receiver input affording desired confidence during single reception of message under effect of hardware parasitic frequency keying in ideal communication channel in absence of fading; P is signal power at receiver input; N_o is single-end spectral power density of additive noise reduced to receiver input; detector channel of receiver with pre-detected character-by-character filtering is, essentially, processor unit functioning to provide multichannel filtering-out matched with keying rate and including parasitic frequency keying, amplitude detection followed by bit-by-bit and frame-by-frame storage and switching either after multichannel filtering-out or after frame-by-frame storage; multichannel filtering-out is effected with different passbands by comb filters. EFFECT: improved design. 3 cl, 4 dwg