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Analog MultiParty Conference Circuit

IP.com Disclosure Number: IPCOM000049907D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Reynes, D: AUTHOR [+2]

Abstract

In known multi-party conference circuits, also designated add-on circuits, the input transformers are connected in parallel leading to great parallel losses and a poor Side Tone Reference Equivalent (STRE) factor. This article describes an analog multi-party conference circuit in which the input transformers are connected in series and in which parallel losses are greatly reduced and the STRE factor improved.

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Analog MultiParty Conference Circuit

In known multi-party conference circuits, also designated add-on circuits, the input transformers are connected in parallel leading to great parallel losses and a poor Side Tone Reference Equivalent (STRE) factor. This article describes an analog multi-party conference circuit in which the input transformers are connected in series and in which parallel losses are greatly reduced and the STRE factor improved.

Referring to the figure which illustrates a three-party conference circuit, the three input lines are connected to the circuit through transformers T1-T3, the PBX network NW and transformers T4-T6. The conference circuit also comprises negative impedance 10 and three impednaces Z, each connected in parallel with one of the transformers T4-T6. When an external party is involved in the conference, switches SW0-SW3 are open and negative impedance 10 compensates for insertion losses. When only internal parties are involved in the conference, switch SW0 is closed and switches SW1-SW3 are open, whereby negative impedance 10 is short-circuited and an impedance Z is connected in parallel with each of transformers T4-T6.

Impedance Z simulates the introduction of a line between two parties by providing a loss of about seven decibels which corresponds to a regular two-internal party connection. The values of impedances Z are calculated to ensure good acoustical performance and, more particularly, a good STRE factor.

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