Pulse or digital communications – Cable systems and components – Transformer coupling
Patent
1993-05-03
1995-05-30
Coles, Sr., Edward L.
Pulse or digital communications
Cable systems and components
Transformer coupling
375224, 370 13, 370 15, H04B 300
Patent
active
054208866
ABSTRACT:
Digital termination equipment for use in signal transmission over a 2-wire subscriber line through an interface transformer includes an impedance unit functionally provided between the 2-wire subscriber line and the interface transformer for generating a high impedance when a current more than a predetermined current value flows therein. A power supply unit is provided having first and second terminals. The first terminal is connected to a winding of the interface transformer for supplying a voltage to the impedance unit through the winding. A current path forming circuit is connected to the impedance unit and to the second terminal of the power supply unit for forming a current path between the impedance unit and the second terminal of the power supply unit when a voltage more than a predetermined voltage value is applied. The power supply unit includes a dc power source and a switch connected in series to the dc power source. The switch is turned on when a local loopback testing is executed.
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patent: 5343461 (1994-08-01), Barton et al.
"T7264 U-Interface 2B1Q Transceiver", AT&T Microelectronics, Jun. 1991.
"LH1465AB ISDN de Termaination IC", AT&T, Nov. 1991.
Coles Sr. Edward L.
Fujitsu Limited
Nguyen Madeleine
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