Fraud prevention in an electronic coin telephone set

US4674114A · kind A · utility

Assignee

• AT&T Technologies Inc., AT&T Bell Laboratories · US

Inventors

• Paul E. Crouch · Freehold, US
• Joseph J. Nahas · Austin, US
• Howard Ng · Kingston, CA

Key dates

• Filing date: Jul 7, 1986
• Grant date: Jun 16, 1987
• Expiry date: Jul 7, 2006

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04M17/023
• WIPO field: Control
• WIPO sector: Instruments

Abstract

In an electronic coin telephone set, a fraud prevention arrangement prevents fraudulent coin tones originating at a telephone transmitter from being provided to a central office over a coin subscriber loop. The arrangement comprises a first and second transmission channel for alternately connecting the transmitter to the central office and also a fraud filter disposed in the second transmission channel. The fraud filter attenuates a selected frequency originating at the transmitter that is indicative of coin deposits. When coin deposits are not required by the central office, the transmitter is connected to the central office through the first transmission channel. When coin deposits are required by the central office, however, the arrangement connects the transmitter to the central office through the second transmission channel thereby avoiding the fraudulent generating of coin tones through the telephone transmitter.