Browse Prior Art Database

Extension Line Circuit

IP.com Disclosure Number: IPCOM000088072D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Morlet, EM: AUTHOR

Abstract

This extension line circuit uses DC (sometimes called galvanic) conductive switches 10, 12 to connect an extension line circuit a-b either across ring buses A-B for application of a ring signal to a-b, or across signal receiver buses C-D for Off/On Hook and dial detection.

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 56% of the total text.

Page 1 of 2

Extension Line Circuit

This extension line circuit uses DC (sometimes called galvanic) conductive switches 10, 12 to connect an extension line circuit a-b either across ring buses A-B for application of a ring signal to a-b, or across signal receiver buses C-D for Off/On Hook and dial detection.

Accordingly, when switches 10, 12 are in the positions shown in dotted lines, there are no series impedances between X-B and a-b except those introduced by windings 14, 16 of line transformer 18, which connects the voice path of a-b to the telephone switching system (not shown) via winding 20. This makes it easy to balance line a-b and its associated ring circuitries and allows the use of a ring signal having a minimum excursion from ground, such as 45 V RMS minus 48 V bias, as shown. Ring trip detector circuit 22, for off-hook detection in the presence of a ring signal, is connected across extension line circuit a-b by high impedance resistors whereby circuit 22 has little effect on the balance of line a-b. Moreover, the balanced nature of the connection of circuit 22 across a-b afforded by resistors 24, 26 and capacitor 28 gives good protection of 22 from longitudinal noise on a-b.

When switches 10, 12 are in their other position, that shown in solid lines, A- B is disconnected from a-b, and ring trip detector circuit 30 is connected across a-b. As in the case of circuit 22, circuit 30 is connected via high impedance resistors 32, 34 in a network including capacitor 36...