FAIL-SAFE CATV SYSTEM CENTER FACILITY

摘要

PO-1-27142M/SK/81 FAIL-SAFE CATV SYSTEM CENTER FACILITY A fail-safe CATV system center facility in which abnormalities in a normal down-data signal transmitter are automatically corrected for so that there is no loss of reception at the terminal units. FM and AM detectors detect the presence ox absence of the normal FSK data signal. The outputs of the FM and detectors are AND'ed together then delayed to control the switch state of a switch which selects between the outputs of the normal down data signal transmitter and a back-up transmitter for coupling through to the table system. The back-up transmitter produces a clock signal which is obtained by modulating a carrier signal having the same frequency as that of the normal down data signal, preferably a frequency shift keyed signal.