05179586 is referenced by 28 patents and cites 2 patents.

An interface unit for interconnecting a telephone central switch to a personal computer. The interface unit receives power and data from the switch over a two wire twisted pair. The data is in a half duplex T.C.M. format and is transformed into standard digital data with the logic "1" and "0" being represented by +5V and 0V respectively. The standard digital data is then arranged into 8 bit words and encoded in either an asynchronous or synchronous manner depending on the type of computer. The interface unit has a line interface circuit which provides the physical interface between the interface unit and the computer. The interface unit has a transmitter circuit which converts the +5V and 0V digital signals to -5V and +5V, respectively. These values are recognized by the computer as logic "1" and "0". The interface unit also has a receive circuit which takes the computer output signals (between -5 and -12V for logic "1" and between +5 and +12V for logic "0") and converts them back into standard digital format.

Title
Line interface circuit
Application Number
7/668613
Publication Number
5179586
Application Date
March 13, 1991
Publication Date
January 12, 1993
Inventor
Michael C G Lee
Ottawa
CA
Agent
Smart & Biggar
Assignee
Northern Telecom
CA
IPC
H04M 1/00
H04M 11/00
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