Electronic Telephone Switching System Research Articles

Design of a Microprogram Control for a Processor in an Electronic Switching System

The processor in an electronic telephone switching system must be designed to efficiently and reliably process telephone calls. Because of the extended life span of a telephone switching system and the nature of the function it provides, it is advantageous to build a great deal of flexibility into the processor design. This paper provides details of a microprogram control design philosophy for the development of a medium-size processor <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∗</sup> that provides the required flexibility. The aspects of the microprogram control that make it very suitable for the design of a processor in a fault-tolerant system are also described.

Large systems: EWS: Germany's answer to ESS: Stored-program control is at the heart of the Deutsche Bundespost's electronic telephone switching system

Stored-program control is at the heart of the Deutsche Bundespost's electronic telephone switching system.

Electronic Switching Systems in Japan

A recently introduced large-size commercially available electronic switching system has versatility in application to different hierarchies of switching stages and is available not only in the telephone systems, but for forthcoming new telecommunication services such as video telecommunications, data applications, mobile radio telephones, etc. Successive developmental programs are now in progress for remote control switching systems, a small-medium-size electronic switching system and data-switching systems. In the international telecommunication field, an electronic telegraph switching system has been completed and electronic telex and telephone switching systems and a data-switching system are now under development. This paper describes some features of various electronic switching systems available in Japan for domestic and international telecommunications.

Development of a Multichannel PAM Telephone Transmission System

This paper outlines the design features, principles of operation, and performance characteristics of a voice transmission path employed in an electronic telephone switching system. The transmission path is two-wire, bidirectional, and incorporates PulseAmplitude Modulation (PAM) as a means of interconnecting the subscribers' line circuits. The system provides facility for 100 simultaneous conversations or "links" in the form of 100 discrete time positions. The techniques employed for supervising and signaling the subscriber's line are also described.

Storage and Switching Circuits for an Electronic Telephone System

Sonic wire delay lines are used for the storage functions and transistor switching circuits for the logic functions comprising the common control of this electronic telephone switching system. Because only short-term storage of transient information (identity of the two parties during a telephone conversation) is required, sonic delay lines are uniquely suitable as storage elements. The use of modern high-speed transistors results in simple and reliable saturated-mode switching circuits operating at a clock frequency of 1 Mc/s.

Impulse analysis and common control in an electronic telephone switching system

This paper discusses the conversion of telephone-line supervision signals into digital logic signals, and the subsequent storage and control of the dialed information, in a telephone switching system using time-division multiplex techniques. Emphasis is on the analyzed-signal timing tolerances and minimization of the logic control functions of the register. Reuse of storage elements for multiple functions on a time discrimination basis and the elimination of logic stages to reduce series delay are also discussed.

Automatic trouble diagnosis of complex logic circuits

This paper deals with the problem of maintaining the most complex portion of an experimental electronic telephone switching system, the central control. New and more effective automatic trouble detection and diagnostic techniques were used. In order to utilize these techniques effectively, a maintenance dictionary — that is, a table relating trouble indications with corresponding faulty plug-in package — had to be produced. The system itself was utilized to create this dictionary. More than 50,000 known faults were purposely introduced into the central control to be diagnosed by its diagnostic program. The corresponding test results were then recorded via a high-speed output. Finally, these test data were sorted and printed in dictionary form by a computer.

Automatic Trouble Diagnosis of Complex Logic Circuits

This paper deals with the problem of maintaining the most complex portion of an experimental electronic telephone switching system, the central control. New and more effective automatic trouble detection and diagnostic techniques were used. In order to utilize these techniques effectively, a maintenance dictionary, i.e., a table relating trouble indications with corresponding faulty plug-in package, had to be produced. The system itself was utilized to create this dictionary. Over 50,000 known faults were purposely introduced into the central control to be diagnosed by its diagnostic program. The corresponding test results were then recorded via a high speed output. Finally, these test data were sorted and printed in dictionary form by a computer.

Logical control of an electronic crosspoint PABX

Recently completed, after 15 months' work by members of Automatic Electric Laboratories, Inc., is a new electronic telephone switching system which will accommodate 100 local subscribers and 20 trunks emanating from an electromechanical exchange.1 Ten of the trunks are PBX (private branch exchange) trunks and ten are 2-way dial trunks. Four operator lines have been established, not only as intermediate terminations for the PBX trunks, but also to provide special services for local subscribers. A 6-position meet-me conference facility is reinforced by a progressive or chain conference feature. Provisions have been made for trunk transfer, trunk restriction, night service, and operator intercept on unequipped lines.2

Semipermanent Storage by Capacitive Coupling

The need arises for reliable, economical high-speed, semipermanent stores for electronic-telephone switching systems, as well as for modern digital computers. A semipermanent or fixed store is one in which the stored information may not be changed by the machine that is able to consult it. These stores provide data security for such information as operational programs and test routines. A random-access store system where the memory elements consist of a matrix of printed capacitors has been developed. The store has a cycle time of 3 Asec and contains 1024 words each 34 bits long. The access circuits developed enable one to utilize a matrix arrangement of components where a need exists for stores of thousands of words. These circuits consist of diodes and biased square-loop ferrite cores in the input, and magnetic gates, utilizing three transformers in a novel arrangement, in the output.

Outlines of a t.d.m. two-wire telephone switching system and its control

The application of certain basic principles of switching and logic system design in electronic telephone switching systems is illustrated in an outline description of a fully-solid-state switching system for exchanges having some 10 000 lines and 1000 junctions. Speech transmissionis ensured on a one-wire time-multiplex p.a.m. basis using the principle of resonant transfer between modem circuits.A particular arrangement of the highway interconnecting network reduces the total number of cross-points to less than 1.2 per line and 2.5 per junction for speech and signalling. Although unbalanced multiplex highways are used throughout, the problem of inter-highway crosstalk can be mastered without particular difficulties, while the overall transmission losses can be reduced to 1.7 dB.Central control has been conceived as a separate data-processing system using ferrite stores and semiconductor logic at relatively low speeds, determined mainly by the real-time requirements of dial-pulse detection and supervision.Outstanding flexibility and design facility has been achieved by the large-scale use of semi-permanent information stores for translation, hunting and programme-controlled logic.

The capacitive semi-permanent information store and its uses in telephone exchanges

A new device is described for storing semi-permanent information, making use of patterns of capacitive couplings at the cross-points between rows and columns of a matrix arrangement. These patterns may easily be changed manually according to the information to be stored. Printed wiring techniques are used throughout, including the capacitive cross-point elements.Basically the new device acts as a code translator, and accordingly it has a wide field of application as a library information store in any data processing systems. Specific examples are given of its adaptability in electronic telephone switching systems, with the object of greatly extending their facilities and generally increasing their flexibility.

Considerations pertaining to the design of an electronic telephone switching system

The U. S. army signal Corps required a basic telephone switching system which could fulfill the functions of a local central office and provide the basis for a long distance (LD) switching center. In addition, a complete switching network was required, built up of a series of local and LD switchboards.

System Design of the Flying Spot Store

The flying spot store is a versatile and efficient semipermanent information storage system developed for use in the electronic telephone switching system. Because of the form of the store, many variables enter into system design. In this paper the factors which control speed, capacity, number of channels, physical size and probability of error in readout are discussed. It is shown that these factors are related to the intended application for the store, to the form of the store and to device parameters. A number of scaling operations which involve exchanges between system parameters such as speed and capacity or between system and device parameters are given.

A High-Speed Barrier Grid Store

This paper describes a high-speed random access memory developed to serve an experimental electronic telephone switching system. The memory uses a barrier grid type electrostatic storage tube which is incorporated in a complete general-purpose store with a capacity of 16,384 bits. Random access to any bit together with a full storage cycle of reading and writing is complete in 2.5 microseconds, permitting a 400-kc repetition rate. Experience with this store indicates that barrier grid storage can provide stable, compact, economical memory for data handling systems.

An Experimental Switching System Using New Electronic Techniques

This is the first of a series of articles describing an experimental electronic telephone switching system employing a number of new techniques. These include use of a stored program, a network employing gas tube cross-points, time-division common control and large-capacity barrier grid tube and photographic storage systems.

Cold Cathode Gas Tubes for Telephone Switching Systems

Cold cathode gas tubes perform both switching and memory functions in telephone switching systems. One measure of the performance of a switching diode is the switching voltage gain, defined in terms of the characteristics of the device. Some of this gain must be sacrificed in order to increase the switching speed in a way which is analogous to the gain-bandwidth property of a conventional amplifier. In this paper, methods of achieving a high switching-voltage gain are described in terms of the gas discharge processes. An example is given of an application of these principles to a tube for use as a switch in series with the talking path in an electronic telephone switching system.