Line interface circuit

Details Line interface circuit Line interface circuit

1991-03-13

1993-01-12

Dwyer, James L.

Telephonic communications

Telephone line or system combined with diverse electrical...

Having transmission of a digital message signal over a...

379442, 307475, 375 76, H04M 1100, H04M 100

Patent

active

051795868

ABSTRACT:
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.

REFERENCES:
patent: 4339727 (1982-07-01), Kage et al.
patent: 4947406 (1990-08-01), Yokoyama
Telesis, vol. 16, No. 2, published by Bell-Northern Limited in 1989, Cover page and pp. 5 through 29.

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