Communications: electrical – Continuously variable indicating – With meter reading
Patent
1981-10-05
1985-01-22
Brown, Thomas W.
Communications: electrical
Continuously variable indicating
With meter reading
179 18AH, 179 18FA, H04M 322
Patent
active
044954948
ABSTRACT:
A detector circuit detects one of two impedances presented by a communication line for each one of a plurality of operative modes. The circuit comprises a network having three parallel branches. The first includes two serially connected resistors which develop a reference potential in response to current flowing in the line. The second branch includes two oppositely poled light-emitting diodes (LEDs) which form a sensor to detect current flow in the line in either direction. The third branch includes a varistor to limit the magnitude of unexpected potentials applied to the sensor. When the magnitude of the reference potential is sufficient to forward bias either LED and the magnitude of the current is greater than a predetermined level, one of the LEDs will generate an output signal representative of one impedance of the line. Otherwise, the LEDs generate a second output representative of the other impedance of the line in a particular operative mode. In addition, a switch selectively controls the amount of current applied to the sensors by reconfiguring the network. In such instances, both of the resistors are directly connected to a source of potential with one resistor acting as a current limiter.
REFERENCES:
patent: 3819866 (1974-06-01), Hawley
patent: 4079208 (1978-03-01), Rogers et al.
patent: 4099032 (1978-07-01), Roge et al.
patent: 4254305 (1981-03-01), Treiber
patent: 4282407 (1981-08-01), Stiefel
patent: 4282408 (1981-08-01), Stauers
patent: 4289933 (1981-09-01), Henry
Bell Telephone Laboratories Incorporated
Brown Thomas W.
Godlewski R. J.
Visserman P.
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