Circuit arrangements in telephone apparatus

Details Circuit arrangements in telephone apparatus Circuit arrangements in telephone apparatus

1974-04-10

1976-05-11

Claffy, Kathleen H.

H04M 144

Patent

active

039565963

ABSTRACT:
A pushbutton telephone semiconductor dialling circuit power supply comprising a capacitor fed by a diode bridge placed in series with the line looping circuit during dialling. The capacitor size is chosen to charge to at least minimum circuit supply voltage during make periods of line looping, and to keep the circuit supplied during break periods. A constant current charging circuit may be employed to charge the capacitor from the bridge to improve performance, with a diode to power the circuit directly from the bridge while the capacitor is still charging.
The microphone-bridging off-normal contacts may be replaced by a transistor switching circuit.

REFERENCES:
patent: 3601552 (1971-08-01), Barnaby et al.
patent: 3787639 (1974-01-01), Battrick
patent: 3856982 (1974-12-01), Lawson

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