Call-signal receiver for station of telecommunication system

Details Call-signal receiver for station of telecommunication system Call-signal receiver for station of telecommunication system

1978-01-23

1979-05-15

Cooper, William C.

H04M 302

Patent

active

041549899

ABSTRACT:
A receiver for call signals, designed to actuate an electro-acoustic transducer such as a ringer in response to incoming alternating voltages of low amplitude and relatively high frequency (e.g. 400 to 450 Hz) or high amplitude and relatively low frequency (e.g. 20 t0 50 Hz), includes a detector for the high-frequency signal and an integrating threshold circuit for the low-frequency signal connected in parallel across a transmission line. The detector is preceded by a phase-locking circuit including a local oscillator of variable frequency adapted to latch on to the high-frequency signal. The presence of either type of call signal activates, through the detector or the threshold circuit, a binary pulse counter stepped by the squared output of the local oscillator to generate a low-frequency square wave subharmonically related to the oscillator frequency which periodically unblocks a gate circuit for the passage of the oscillator output to operate the transducer.

REFERENCES:
patent: 3808379 (1974-04-01), Lind
patent: 4042786 (1977-08-01), Freimanis

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