Active speech network circuit for a telephone set

US4332984A · kind A · utility

Assignee

• Bell Telephone Laboratories, Inc. · US

Inventors

• Paul C. Davis · Reading, GB
• Raymond G. Jackson · Indianapolis, US
• Kenneth F. Sodomsky · Reading, US
• Dennis L. Whitson · Corydon, US

Key dates

• Filing date: Dec 13, 1979
• Grant date: Jun 1, 1982
• Expiry date: Dec 13, 1999

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04M1/585
• WIPO field: Telecommunications
• WIPO sector: Electrical engineering

Abstract

In a subscriber telephone set, an active speech network provides a sidetone signal and for equalization of the transmit and receive signals at the tip and ring line port and also maintains the dc voltage at a substantially constant level at this port. The network is compatible with conventional telephone sets and operation on long loops in parallel with such sets is provided for. Internal circuitry (320) within the network check both loop current and tip-to-ring voltage to ensure that both are of a magnitude sufficient for a tone signaling dial (301) to properly generate tone signals before enabling the dial.