Method and apparatus for preventing pin fraud on coin telephones that use battery reversal pulses to meter charges
US5757896A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 31, 1996 |
| Grant date | May 26, 1998 |
| Priority date | — |
| Expiry date | May 31, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M17/02
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Pin fraud of battery reversal pulse metered sophisticated coin telephones is detected and prevented by the method and apparatus of the invention. By carefully monitoring within the switch office the loop current that is flowing in the 48 volt battery circuit, especially in the more positive terminal portion of the 48 volt battery circuit, loss of current to a fraud ground at a remote coin telephone can be detected. Once a fraud ground is detected, the call is terminated. The current detector of this method and apparatus can also be used to terminate a call for the normal on-hook break of the loop current. A convenient location in the switch office and an inexpensive component configuration make the addition of this pin fraud detection and prevention apparatus very cost effective.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.