Telephone line feed

Details Telephone line feed Telephone line feed

1980-12-03

1984-02-14

Robinson, Thomas A.

179 16F, H04M 100, H04B 316

Patent

active

044318693

ABSTRACT:
In a telephone line feeding arrangement, the line current is monitored by a multi-resistor network (R.sub.p R.sub.s) and the output of the network applied to the inputs of an operational amplifier (A3). The output of this amplifier, which is a voltage whose value depends on the line current, is compared by a comparator (A4) with a reference voltage (V.sub.R) to produce a control voltage for a variable voltage (VVS), the output of which provides line feeding voltage.
In an alternative, the monitoring is effected by connecting the two line wires each via a resistor to one of the inputs of an operational amplifier (A6) whose output is a voltage dependent on line voltage. This voltage is applied to an input of another operational amplifier (A7) where it is in effect added to a reference voltage (V.sub.R). The output of this amplifier (A7) is used to control the variable voltage source (VVS), which in turn controls a constant current source (CCS) whose output provides line current.

REFERENCES:
patent: 4037066 (1977-07-01), Kiko
patent: 4268723 (1981-05-01), Taylor

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