Toll fraud detector
US4159400A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 10, 1978 |
| Grant date | Jun 26, 1979 |
| Priority date | — |
| Expiry date | Aug 10, 1998 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M3/38
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A detector for a "Black Box" toll fraud is connected to circuits at the called party's central office and comprises a relay connected in series with the called subscriber's tip (T) lead, a fraudulent call register or indicator, and a normally open time delay switch with a timer actuated by a ringing signal on the ring (R) lead, which switch closes after a predetermined delay interval (ten seconds) to cause energizing of the register. The flow of direct current in the T lead incident to the called party going off-hook energizes the relay and deactivates the switch. The control (C) lead of the central office subscriber circuit is grounded by the off-hook state of the calling party's telephone and is connected to the register by closing of the delay switch, the indication of a fraudulent call being made by the register on removal of ground from the C lead, i.e., when the calling party goes on-hook. A terminal for connecting to the starting mechanism of a recorder is also provided in parallel with the time delay switch for turning the recorder on so that a permanent record of the fraudulent call may be made. In a modified form of the invention, means are provided to prevent indication …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.