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Ringing Circuit for Private Branch Exchange

IP.com Disclosure Number: IPCOM000081477D
Original Publication Date: 1974-Jun-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Papo, M: AUTHOR

Abstract

Implementing conventional ringing circuits of Private Branch Exchanges (PBX) involves a number of difficulties, particularly because the telephone set bell needs AC power supplies which require relatively high voltages (up to 100 V). Thus, at the interfaces between the PBX and the telephone lines, each pack requires protection circuitry.

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Ringing Circuit for Private Branch Exchange

Implementing conventional ringing circuits of Private Branch Exchanges (PBX) involves a number of difficulties, particularly because the telephone set bell needs AC power supplies which require relatively high voltages (up to 100
V). Thus, at the interfaces between the PBX and the telephone lines, each pack requires protection circuitry.

In order to avoid these drawbacks, a solution is suggested in which the ringing power supply is removed from the PBX.

According to this solution, the PBX comprises a ring control tone sender RS, which may be selectively connected to the primary winding of any of the line transformers LT. Each office corresponding to each telephone set comprises an independent ringing circuit RC, which controls the activation of the bell or buzzer B associated with the telephone set TS, upon detection of the tone received from tone sender RS.

Ringing circuit RC includes a symmetrical tone detector TD, an AND circuit, and a driver D which directly controls bell B. The power supply PS which is necessary to operate ringing circuit RC is derived from the standard 220 V AC mains, or any other appropriate local power supply. This solution saves circuitry and may be used with any type of telephone set, without any modification thereof.

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