Browse Prior Art Database

Low-Cost Time Division Switch Module for Telephone Switching Applications

IP.com Disclosure Number: IPCOM000047162D
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 51K

Publishing Venue

IBM

Related People

Brady, RL: AUTHOR [+2]

Abstract

In contemporary telephone systems, voice and destination selection (dial number) signals are passed through switching exchanges which operate in either a space division or time division mode. Space division systems employ switching matrices which provide continuous circuit connections between linked user port units and may process the voice and selection signals in either analog or digital form. Time division multiplex (TDM) systems generally handle only digital signals, usually in PCM (Pulse Code Modulated) form, and employ time slot interchange units to pass voice and signal traffic between dynamically allocated time slots at incoming (source) and outgoing (destination) ports.

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 51% of the total text.

Page 1 of 3

Low-Cost Time Division Switch Module for Telephone Switching Applications

In contemporary telephone systems, voice and destination selection (dial number) signals are passed through switching exchanges which operate in either a space division or time division mode. Space division systems employ switching matrices which provide continuous circuit connections between linked user port units and may process the voice and selection signals in either analog or digital form. Time division multiplex (TDM) systems generally handle only digital signals, usually in PCM (Pulse Code Modulated) form, and employ time slot interchange units to pass voice and signal traffic between dynamically allocated time slots at incoming (source) and outgoing (destination) ports. A time slot interchange unit generally comprises one or more buffer stores and a commutation controller (which, typically, in today's systems would include a microprocessor) for reading digitized information samples (voice or data) between address locations associated with "source" port time slots and address locations associated with destination port time slots. It is now widely recognized that such interchange units must be reasonably modular in form so that they may be configured inexpensively to accommodate a variety of traffic conditions. The unit architecture described below offers such modularity, and is considered particularly attractive because it employs only "off-the-shelf" vendor components as modular elements. Referring to the drawing, slot interchange unit 1 links TDM highways/channels on N input buses 2 to TDM highways on M output buses 3 (N and M representing variable integers). In order to accommodate voice telephone signals the repeating time slots constituting a highway are each configured to contain 8 bits of digital information (useful to represent either a voice sample digitally encoded in an 8-bit PCM form or an 8-bit byte of non-voice data). Each bus is time partitioned to carry either 20 or 32 channels in conformance with equipment characteristics now widely in use by common carriers in the United States and elsewhere. Information flows from the input buses to the unit 1 and from the unit 1 to the output buses. In two-way phone or data hookups paired users are each assigned two highways (one for transmission and the other for reception). Within the unit 1, information bytes are passed from input bus highways to SERDES (serializer/deserializer) modules 4, thence in bit-parallel byte-serial form to byte wide latches 5, and from the latches 5 into pre-assigned locations in byte addressable RAM (random-access memory) module 6. From the RAM, information bytes are read out to SERDES modules 7 associated w...