1980-11-13
1982-03-30
Robinson, Thomas A.
179 16AA, H04B 158, H04M 1906, H04Q 318
Patent
active
043225861
ABSTRACT:
A line circuit includes a fixed resistance feed consisting of a pair of resistors connected in series with a d.c. power source and tip and ring leads of a communication line. A variable current feed includes a current sink and a current source also connected in series with the d.c. power source and the TIP and RING leads. Energizing current flow in the communication line results as the combination of currents passed by the two feeds. A control circuit determines the currents conducted by the current source and current sink and introduces variations in these currents in accordance with signals for transmission along the communication line. Differences between current flows in the variable current feed and current imbalance conditions on the communication line are accommodated by the fixed resistance feed which also determines the terminating impedance for the communication line.
REFERENCES:
patent: 4004109 (1977-01-01), Boxall
patent: 4041252 (1977-08-01), Cowden
patent: 4174470 (1979-11-01), Seidel
patent: 4178485 (1979-12-01), Cowpland
patent: 4181824 (1980-01-01), Seidel
patent: 4203009 (1980-05-01), Tattersall
patent: 4203012 (1980-05-01), Boxall
XC3419 Subscriber Loop Interface Circuit Motorola Semiconductor, Box 20912, Phoenix, Ariz. 85036.
3081-3082 to 3084-3085 Subscriber Line Interface Circuits ITT North Deerfield Beach, Fla. (1979).
Mein Gordon F.
Terry John B.
Moorhouse J. E.
Northern Telecom Limited
Robinson Thomas A.
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