Browse Prior Art Database

Telecommunications Transmitter/ Receiver with Sidetone Suppression

IP.com Disclosure Number: IPCOM000050268D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Crauwels, GL: AUTHOR

Abstract

This "hybrid" circuit, for two-wire to four-wire linkage, substantially reduces returned outbound energy and offers sidetone suppression without the use of bulky transformers. It also presents proper terminating impedance to the communication line. It can be used in telephone networks and full duplex data communications applications.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 83% of the total text.

Page 1 of 2

Telecommunications Transmitter/ Receiver with Sidetone Suppression

This "hybrid" circuit, for two-wire to four-wire linkage, substantially reduces returned outbound energy and offers sidetone suppression without the use of bulky transformers. It also presents proper terminating impedance to the communication line. It can be used in telephone networks and full duplex data communications applications.

Terminals 1 and 2 connect to two-wire communication line 3 and present terminating impedance ZIN to that line. Amplifier 4 is the driver, and amplifier 5 is the receiver relative to four-wire line 6.

Sidetone suppression is affected by variations in chatacteristic impedance R(L) on communication line 3.

Four sets of equations are required to select component values. They are reproduced on the next page in the form used for telephone network application; in this form resistances are substituted for more general impedances. Equation A satisfies the input impedance ZIN with R4 and R5 assumed to have been selected for minimizing side tones. Equation B satisfies sidetone suppression selection requirements. Equation C determines transmit gain. Equation D determines input gain. Selection of certain components may also be based on amplifier specifications.

It is possible to maximize sidetone suppression for values of RL other than ZIN. This is useful when the specified termination does not equal the actual (R(L)) line impedance (assuming pure resistive impedance).

Another mod...