Browse Prior Art Database

Electronic Hybrid for Telephone using a Differential Amplifier

IP.com Disclosure Number: IPCOM000080014D
Original Publication Date: 1973-Oct-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Appel, U: AUTHOR [+2]

Abstract

This is an electronic hybrid in which an electrical bridge arrangement is balanced, to provide high isolation between incoming and outgoing wire pairs upon application of the incoming signal only, and unbalanced to provide feedthrough from a local telephone signal source to an outgoing line when the source becomes active. It is desirable to terminate each end of an outgoing and incoming wire pair in a hybrid, such as is shown in Fig. 1.

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 73% of the total text.

Page 1 of 2

Electronic Hybrid for Telephone using a Differential Amplifier

This is an electronic hybrid in which an electrical bridge arrangement is balanced, to provide high isolation between incoming and outgoing wire pairs upon application of the incoming signal only, and unbalanced to provide feedthrough from a local telephone signal source to an outgoing line when the source becomes active. It is desirable to terminate each end of an outgoing and incoming wire pair in a hybrid, such as is shown in Fig. 1.

In the prior art, a hybrid was defined as a four-wire circuit with two wire connections, the physical arrangement consisting of two multiwinding transformers serving to connect three signals and a matching network. The three signal paths were, namely, the incoming and outgoing signal wire pair and the telephone handset. Because the circuits were all electromagnetically coupled, a balancing (matching) network was used to prevent high feedthrough. Independent of the hybrid, some coupling is always provided by the telephone handset instrument itself, due to the circuit coupling of the portion of the speaker's signal back to the receiver for "live phone" perception purposes by the telephone user.

Referring to Fig. 2, there is shown a telephone handset 1 magnetically coupled to a hybrid 2 over a transformer 3. A difference operational amplifier 4, which provides a high-input impedance for a null differential signal input applied to its terminals 5, 6 and a lower impedance o...