Interface unit for pushbutton selector

Details Interface unit for pushbutton selector Interface unit for pushbutton selector

1980-05-28

1982-05-11

Konick, Bernard

179 90K, 179 16EC, H04M 144

Patent

active

043295460

ABSTRACT:
An interface unit inserted between a subscriber line of a telecommunication system and a generator of dial pulses, including a signal converter associated with a pushbutton selector and a memory for the temporary storage of selected digits, comprises a rectifier bridge in series with an impedance network which includes a shunt branch with two complementary transistors interconnected in a positive-feedback circuit and a low-threshold Zener diode in series with one of these transistors across which a reduced supply voltage for the pulse generator remains available when the shunt branch becomes conductive with saturation of the transistors upon a closure of the subscriber's hook switch. An enabling signal for the pulse generator is emitted from the shunt branch upon such conduction. An ancillary transistor, with an input connection across a small series resistor of the network, and a further Zener diode in parallel with the shunt path protect the components thereof against overcurrents and overvoltages.

REFERENCES:
patent: 3956596 (1976-05-01), Connolly et al.
patent: 3973084 (1976-08-01), Hovland
patent: 4008379 (1977-02-01), Watkins

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