DOI:10.1049/pi-b-2.1960.0014

出版商:IEE    

年代:1960

数据来源: IET

摘要:

An experimental public service telephone exchange is to be installed at Highgate Wood in North London. It has been developed in order to gain experience of the problems posed by introducing electronic exchanges into the public network. It meets a full and flexible facility schedule, and will test a variety of electronic time-sharing and commoncontrol techniques in the field.Speech and other signals are transmitted over unidirectional highways carrying 100 time-division-multiplex pulse channels. Each connection uses a pair of antiphase channels and is set up through line and inter-highway switches by storing channel pulses in magnetostriction delay lines. Delay lines also form the central feature of common register and supervisory equipments which, by operating with the channel pulses, control the setting up and progress of all calls. Common apparatus selects the channels to be used on all connections which are set up one at a time using information stored on magneticdrum tracks. Such information includes the directory number, meter record, state, class of service and type of each line, together with a library of translations required to route calls over junctions.A diversity of circuit techniques is included in the Highgate Wood exchange, which also incorporates security arrangements and maintenance aids to safeguard service to the subscriber, and to ease maintenance problems. The experience gained during the design, development, manufacture and trials of the system is expected to prove invaluable in progressing towards the telephone system of the future.

DOI:10.1049/pi-b-2.1960.0015

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The trunking of electronic telephone exchanges is not a rigid framework which must be specified before the design of an exchange suitable for the rigours of the public service can be undertaken.Changes are repeatedly needed to accommodate other developments, so that a common basis of various arrangements is sought. For exchanges for which a multiplex system of a large number of channels is suitable the basic arrangement which emerges is that of simple inter-highway switching—the system used for the exchange being installed at Highgate Wood.In many of these systems a problem arises because subscribers sharing the use of a multiplex system cannot share the use of a single channel to communicate with each other. From discussion of varioussolutions it is seen that the method of anti-phase channels used in the Highgate Wood exchange, although simple, is unlikely to be repeated, modern transistors making more economical solutions practicable.The problems of traffic-carrying capacity of these exchanges show a wide gulf between the complexity of accurate theory and the relative simplicity of methods which are useful in practice. These methods have been revised, and are presented in relation to their most useful application—the assessment of the relative merits of different trunking systems.

DOI:10.1049/pi-b-2.1960.0016

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The Post Office and its principal telephone manufacturers have developed jointly an experimental electronic telephone exchange which will be installed at Highgate Wood Exchange in North London. The exchange is designed to operate on time-division-multiplex principles using switched highways, and these techniques are used throughout the common control apparatus. The paper describes the setting up of normal calls and their subsequent control, with particular reference to those parts of the exchange which fulfil the functions of providing speech connections between lines, detecting calling conditions, processing dialled information, selecting the called lines, controlling established connections and metering.

DOI:10.1049/pi-b-2.1960.0017

出版商:IEE    

年代:1960

数据来源: IET

摘要:

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.

DOI:10.1049/pi-b-2.1960.0018

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The design of a 4-wire light-weight electronic automatic telephone system intended for tactical use by the United States Field Army is described. The reasons for the choice of a time-division multiplex system using semiconductors are given. The error-correcting signalling system employed and the means adopted to achieve an easilytransportable rapidly-installed system are described.The system includes a key-sending telephone, local, long-distance and tandem switchboards, and it uses either radio, carrier or a.f. interconnections between switchboards. The components used and the circuit configuration chosen are selected to ensure that the specified military reliability objectives are met. Modular construction is employed in order to simplify maintenance in the field.

DOI:10.1049/pi-b-2.1960.0019

出版商:IEE    

年代:1960

数据来源: IET

DOI:10.1049/pi-b-2.1960.0021

出版商:IEE    

年代:1960

数据来源: IET

摘要:

For signal injection in time-multiplex systems operating on the ‘resonant transfer’ principle two methods are described. In 2-wire systems the injection is accomplished by means of a pulse circuit similar to that of the subscriber but without a low-pass filter. For charging the injector-circuit capacitor in the pause between pulse positions a specially designed signal generator is connected to the circuit by means of a time-controlled pulse contact. The capacitor is always charged to the instantaneous voltage of the signal generator independent of chance residual charges, which may otherwise cause crosstalk.In 4-wire systems a simplified procedure may be adopted. The functions of charging contact and injector contact are here combined in a single pulse contact, which connects the signal generator directly to the receiving highway. This pulse contact closes coincidentally with the subscriber contact, but breaks earlier. Under specific conditions the following functions are obtained: current zero or minimum at the instant when each contact breaks. Voltage maximum on the subscriber capacitor at the instant when the subscriber contact breaks while simultaneously a voltage minimum on the highway tuning capacitance nears zero. Finally some methods for generating sinusoidal or composite signals are described.

DOI:10.1049/pi-b-2.1960.0022

出版商:IEE    

年代:1960

数据来源: IET

摘要:

Expressions are derived for the inter-highway crosstalk due to capacitive coupling in the highway-interconnecting network as functions of the parameters of the transmission path and the time shift between the switching control pulses.An analogous relation can be derived for the inter-highway crosstalk due to the mutual inductance between neighbouring highways; however, this kind of coupling can easily be reduced to negligible values.Measured crosstalk values are in close agreement with the theoretical results.

DOI:10.1049/pi-b-2.1960.0023

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The paper deals with the design of a current-operated t.d.m. transmission path suitable for use in an electronic telephone exchange employing 4-wire transmission. Direct replacement of the thermionic valve circuits used in the proposed Highgate Wood exchange with equivalent transistor stages raises difficulties. These are enumerated, and the advantages of current operation are outlined. A detailed description is given of typical circuit-elements including modulators and demodulators. Finally, a brief outline of the performance is included.

DOI:10.1049/pi-b-2.1960.0024

出版商:IEE    

年代:1960

数据来源: IET