Line power control circuit for pay station telephone
US4942604A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 22, 1988 |
| Grant date | Jul 17, 1990 |
| Priority date | — |
| Expiry date | Jun 22, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M17/023
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.