Telephonic communications – Subscriber line or transmission line interface – Protective circuit
Patent
1988-06-22
1990-07-17
Lev, Robert
Telephonic communications
Subscriber line or transmission line interface
Protective circuit
379413, 379145, H04M 1900
Patent
active
049426044
ABSTRACT:
An interface (10) is disclosed for coupling a conventional pay station telephone (12) to a telephone switching system (16). The interface (10) provides supervision signal detection functions normally provided by a switching system, and thus can be connected thereto by a less costly business line (28). The interface includes processor controlled tone generators (72, 76) and detectors (73, 74, 81, 106, 108) for detecting tones and voltages transmitted by either the telephone (12) or the switching system (16). The interface (10) further includes a detector (106) and a procedure (FIG. 8) for providing an answer call indication. Coin collection or return is controlled by the interface (10) depending on the status of the call which is also determined by the interface (10). Further, a fail-safe relay will disconnect the phone from the tip and ring lines in the event of station irregularities. If the fail-safe relay operates during a phone call, the connection is maintained until the end of the call by power fail call holding relays.
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Hoback Conaway K.
Smith Benjamin A.
Digital Telecommunications Systems, Inc.
Lev Robert
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