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The Rolm Computerized Branch Exchange: An Advanced Digital PBX

IP.com Disclosure Number: IPCOM000131404D
Original Publication Date: 1979-Jun-01
Included in the Prior Art Database: 2005-Nov-10
Document File: 10 page(s) / 43K

Publishing Venue

Software Patent Institute

Related People

James M. Kasson: AUTHOR [+3]

Abstract

[Figure containing following caption omitted: The private branch exchange, employing pulse- code modulation and computer-controlled time-division multiplexing, is an increasingly popular tool for enhancing the flexibility and reducing the cost of business telephone operations.] Advances in computer and semiconductor technology have provided the means for a new generation of business- oriented circuit-switching systems with capabilities dramatically exceeding those of conventional private branch exchanges.* The Carterfone decision) 2 and subsequent FCC rulings, by opening the business communications market to competition, have provided the motive for new companies to enter the field and for present suppliers to improve their products. Advanced PBXs are universally computer controlled, using machines ranging from 8-bit microprocessors to 32-bit medium-scale computers, and perform functions sufficiently complex to require operating systems and applications software of significant scale. The most common switching method for PBXs introduced in the last few years is time-division multiplexing of sampled digital representations of the input signal. When the digital signal represents the value of the signal at the instant of sampling, the encoding technique is referred to as pulse-code modulation, or PCM. [Footnote] *A Private Branch exchange, or PBX, is a circuit- switcbing system which provides service to one user organization. Usually located at the users' sites, PBXs have traditionaUy provided basic voice switching services. The traditional PBX has three classes of ports: 41) station users or extensions, which are telephones connected directly to the switch; (2) attendants; and 13) trunks, which connect the switch to the public switched telephone network or to other private networks. The PBX usuaUy routes incoming cans to attendant positions, from which they may be extended to station users; aUows for station-to-station caning without the use of the telephone network; and aUows station users to access the telephone network for outgoing cans. The designers and manufacturers of modern PBX equipment have three primary objectives for their systems. First, the life-cycle cost of the system should be as low as possible. The life-cycle cost of a PBX may be broken down into the following components: initial purchase cost

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

This record contains textual material that is copyright ©; 1979 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Contact the IEEE Computer Society http://www.computer.org/ (714-821-8380) for copies of the complete work that was the source of this textual material and for all use beyond that as a record from the SPI Database.

The Rolm Computerized Branch Exchange: An Advanced Digital PBX

James M. Kasson

Rolrn Corporation

    (Image Omitted: The private branch exchange, employing pulse- code modulation and computer-controlled time-division multiplexing, is an increasingly popular tool for enhancing the flexibility and reducing the cost of business telephone operations.)

Advances in computer and semiconductor technology have provided the means for a new generation of business- oriented circuit-switching systems with capabilities dramatically exceeding those of conventional private branch exchanges.* The Carterfone decision) 2 and subsequent FCC rulings, by opening the business communications market to competition, have provided the motive for new companies to enter the field and for present suppliers to improve their products. Advanced PBXs are universally computer controlled, using machines ranging from 8-bit microprocessors to 32-bit medium-scale computers, and perform functions sufficiently complex to require operating systems and applications software of significant scale. The most common switching method for PBXs introduced in the last few years is time-division multiplexing of sampled digital representations of the input signal. When the digital signal represents the value of the signal at the instant of sampling, the encoding technique is referred to as pulse- code modulation, or PCM.

1

The designers and manufacturers of modern PBX equipment have three primary objectives for their systems. First, the life-cycle cost of the system should be as low as possible. The life-cycle cost of a PBX may be broken down into the following components:

initial purchase cost

configuration and installation

maintenance, changes, and additions

attendant and station-user labor costs

network usage charges

Second, the design of the PBX should allow for future enhancements in features and switching capability. The PBXwiR become the focal point for many types of business communication besides voice: facsimile or character-mode electronic mail and computerterminal

1 *A Private Branch exchange, or PBX, is a circuit- switcbing system which provides service to one user organization. Usually located at the users' sites, PBXs have traditionaUy provided basic voice switching services. The traditional PBX has three classes of ports: 41) station users or extensions, which are telephones connected directly to the switch; (2) attendants; and 13) trunks, which connect the switch to the public switched telephone network or to other private networks. The PBX usuaUy route...