Browse Prior Art Database

Line Scanning

IP.com Disclosure Number: IPCOM000093451D
Original Publication Date: 1967-Sep-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Garcia, J: AUTHOR [+2]

Abstract

This system is for scanning telephone lines in a private branch exchange with a space division switching network. The scanning is performed from the junctor side by detecting the presence or absence of a nonaudible signal of, e.g., 15 kc/s.

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 76% of the total text.

Page 1 of 2

Line Scanning

This system is for scanning telephone lines in a private branch exchange with a space division switching network. The scanning is performed from the junctor side by detecting the presence or absence of a nonaudible signal of, e.g., 15 kc/s.

The telephone line is connected between -48 volts and ground. Each telephone line is connected to the switching network, composed of cross-points, through line transformer TR. The emitter of transistor T2 is connected to the telephone line via resistor R1. The collector of T2 is connected to ground through load resistor R2 and to the switching network through capacitor C which blocks DC components. The base of T2 is connected to a common bus carrying a signal of 15 kc/s delivered by a pilot frequency sender.

In the on-hook condition, i.e., telephone set replaced, T2 is cut off and in the off-hook condition the telephone set is lifted. A DC current flows through the telephone line. T2 applies a 15 kc/s signal to the corresponding network inlet, point A. This signal is detected by a pilot frequency detector branched on feeder transistor T1 of the junctor. A junctor latch with these two inputs set and reset controls T1.

The pilot frequency detector is composed of filter L1 and C1, transistor T3 working in class A, rectifier diode D, integrating capacitor C2, and transistor T4, the output of which delivers the detection signal.

The telephone line scanning is performed as follows. A free junctor is chosen and all nonb...