Stored Program Control Research Articles

The5ESSSwitching System: Operations, Administration, and Maintenance Capabilities

The 5ESS™ switching system is a digital, time-division switching system that is being introduced into a multiplicity of operating environments — local, toll, private networks, and stand-alone applications. Many of these operating environments are currently dominated by analog, space-division switching systems. Furthermore, the 5ESS switching system is being introduced into environments in which there have been increasing trends toward centralization and mechanization of operating procedures through the use of minicomputer-based support systems. The 5ESS switching system has been designed to allow a smooth incorporation into these mechanized operating environments, while still retaining features needed for stand-alone operations in less mechanized environments. This paper describes the operational features, both administrative and maintenance, of the 5ESS switching system. The emphasis is on the features that differ from those of earlier stored program control switching systems. These include features that represent enhancements over those of earlier systems, differences mandated by a digital, time-division technology, and features designed to more readily adapt to operations support systems.

Fault diagnosis of SPC switching systems based on structure and signalling

The paper presents a new approach to fault diagnosis of stored program controlled (SPC) switching systems. It uses the functional behaviour of SPC systems to model faults. This method uses circuit, structure descriptions and call processing programs to generate automatically the data required for fault analysis and avoids fault simulation.

Approximate Analysis of a Generalized Clocked Schedule

Clocked schedules represent an important method of task scheduling for computer systems with real-time applications. In this paper we consider a generalized class of clocked schedule that includes those used in many stored program control switching systems. Key performance measures for this class are discussed, and an analytic approximation method for analyzing certain of these measures is given. This approximation method is most applicable in evaluating long-term delays. (A companion paper by Doshi addresses short-term delays for systems with extremely time-critical tasks.) Comparisons are made with exact numerical results (obtained using the method presented in a companion paper by Ackroyd), detailed simulation models, and field data.

Fault diagnosis of SPC switching systems based on structure and signalling

The paper presents a new approach to fault diagnosis of stored program controlled (SPC) switching systems. It uses the functional behaviour of SPC systems to model faults. This method uses circuit, structure descriptions and call processing programs to generate automatically the data required for fault analysis and avoids fault simulation.

The MERLINTMCommunications System

The MERLINTMCommunications System is a family of architecturally consistent small-business communications systems. The architecture is a star configuration with a central 8 bit microprocessor in the switch or Control Module for control of all telephone functions. The telephones and the processor exchange information over a proprietary four-pair protocol in a 24 bit message. In the Control Module, all I/O functions are memory mapped and under software control. The switch is an analog space-division solid-state crosspoint matrix, and the system capacities range from two CO lines and six telephones to eight CO lines and twenty telephones. Unlike many of its contemporaries, this system is designed to be installed, administered, and maintained by customers, although many users can be expected to opt for full-service support. Features and options can be added by a family of plug-in cartridges allowing the whole system to be sold directly from a catalog to a customer with limited training. Another design intent, simplified by stored-program control, is to incorporate many of the more popular and useful call-handling features of larger PBX's. A list of these is given in the Appendix. The stored program containing those features resides in a plug-in cartridge. This article will highlight the electrical and physical design of three of the MERLIN communications systems (CS): models 206, 410, and 820.

Basic briefing: choosing a PABX

Traditionally the private telephone exchange functions as a switch to connect a group of extension users in an organisation to the public switched telephone network (PSTN) and to connect these extension users to each other — and that's all. The installation of a new private automatic branch exchange (PABX) represents not only a major capital investment for a company, but the opportunity to benefit from recent great advances in telecoms. In theory the choice of exchange is straightforward: the stored program control (SPC) type PABX (or call connect system as it is sometimes known) will supersede both manual exchanges, with or without separate private automatic exchanges (PAXs), and Strowger electro‐mechanical exchanges. In practice the selection process is becoming increasingly complex.

Intelligent PLL Using Digital Processing for Network Synchronization

By combining the advanced technologies of a crystal oscillator, LSI, and a computer, an intelligent phase-locked loop (PLL) which uses digital processing (DP) can be created. This kind of PLL, which is referred to here as DP-PLL, includes a microprocessor and a digitally controlled crystal oscillator. It features excellent performance and countermeasures for disturbances of the input signal by stored program control. In this paper, implementation and performance of the DP-PLL are presented with the aim of application in a master-slave network synchronization system.

Total Network Data System: Central Office Equipment Reports for Stored Program Control Systems

Stored Program Control System Central Office Equipment Reports (SPCS COER) is one of the earliest of the family of Operations Systems. Deployed on a centralized time-shared system, it produces engineering and administrative reports for Stored Program Central Office Equipment. This paper describes the user needs that motivated the design of SPCS COER. It traces the development of the system from a joint experiment of Bell Laboratories and the New York Telephone Company's Manhattan Engineering Department to the present system serving over 2800 electronic central offices from three centralized Amdahl V6 computers. We explain the functional system design from the user's point of view and outline the structure of the software, emphasizing the “tools” approach that is central to the development. The project management featured a research and development style, which we call the “whole-job” approach and discuss in some detail. Finally, we explore possible future directions for the project.

Traffic Service Position System No. 1B: Retrofitting the Processor

At the end of 1981, over 150 Traffic Service Position System No. 1 (TSPS No. 1) offices were in service, equipped with Stored Program Control No. 1A (SPC 1A) processors. Some of these sites had reached the system capacity with respect to real time or memory. The new SPC 1B, which contains a 3B20 Duplex (3B20D) Processor and a Peripheral System Interface (PSI), provides the TSPS No. 1B with additional processor capabilities for additional capacity and future features. This article discusses the techniques used for achieving a smooth retrofit from the TSPS No. 1 to TSPS No. 1B with virtually no interruption of call processing. Special procedures and tools were developed to introduce the SPC 1B onto existing buses and to verify the interfaces with existing peripherals by means of a cycle-stealing mechanism, while the SPC 1A continues to handle call processing. These procedures were used successfully at the first such retrofit in Redwood City, California, on March 13, 1982. During 1982, 34 additional sites will be retrofitted by Western Electric to accomplish the initial phase of the planned retrofits to TSPS No. 1B.

Traffic Service Position System No. 1B: Real-Time Architecture Utilizing the DMERT Operating System

The Traffic Service Position System No. 1B (TSPS No. 1B) architecture was conceived to increase performance significantly for future features and traffic growth. The design preserves the TSPS No. 1 software with minimal changes. At the same time, the 3B20 Duplex Processor (3B20D) used in TSPS No. 1B provides additional processor peripherals and a modern programming environment with a real-time operating system. This paper describes how the TSPS No. 1 software, initially designed to run on the Stored Program Control No. 1A (SPC 1A), executes on the SPC 1B of the TSPS No. 1B. The SPC 1B is a 3B20D tailored for the TSPS application and provides an SPC 1A environment by directly emulating its instruction set. The paper also presents major TSPS application processes and their interaction with the emulated TSPS process and the Duplex Multi-Environment Real-Time (DMERT) operating system of the SPC 1B. In addition, the paper describes the integration of TSPS maintenance software into the DMERT maintenance structure.

Traffic Service Position System No. 1B: System Description

The Traffic Service Position System No. 1B (TSPS No. 1B) is the first field application of the Bell System's new 3B20 Duplex Processor (3B20D) in the emulation mode. The 3B20D Processor replaces the existing Stored Program Control No. 1A (SPC 1A), while retaining the existing TSPS periphery and software. A key factor is the ability to switch between the emulated software and the 3B20D native software within a single process with a single instruction. This allows the flexibility of adding software in either environment as appropriate.

Traffic Service Position System No. 1B: Hardware Configuration

The Traffic Service Position System No. 1B (TSPS No. 1B) was developed by replacing the Stored Program Control No. 1A (SPC 1A) with the SPC 1B, consisting of a 3B20 Duplex Processor (3B20D) and a Peripheral System Interface (PSI). The PSI was designed to interface the 3B20D Processor technology with the existing TSPS peripheral system. This article describes the differences in technologies between the SPC 1A and SPC 1B, the hardware design required to overcome these differences, and the fault recovery and diagnostic software development required to integrate the new hardware into the maintenance structure of the TSPS No. 1B.

Traffic Service Position System No. 1B: Switching Control Center System Interface

Over the years, the centralization of the maintenance and operation of Stored Program Control Systems (SPCS) has proved to be an economically attractive and effective methodology. At the core of the centralized maintenance plan is the Switching Control Center (SCC), which has responsibility for the surveillance and control of a number of SPCS. This center is supported by the Switching Control Center System (SCCS), which is a minicomputer-based system that provides automation of, or mechanized support for, the functions of the SCC. Since SCCS support for the Traffic Service Position System No. 1 (TSPS No. 1) was already available, these capabilities needed to be carried forward to support the operation and maintenance of TSPS No. 1B. In addition, the use of the new 3B20D Processor with a new craftperson interface allowed for a number of improvements and extensions. The SCCS interface to TSPS No. 1B has made use of new technology and techniques by incorporating microprocessors, video terminal interfaces, and BX.25 protocol in the design. The result is a flexible interface with software-driven craft displays.

Design and Development of Electronic Telex Systems in India

The paper deals with the design and development of Electronic Telex Systems in India right from its inception in the country. System design criteria for electronic telex are different from those for electronic telephone exchange due to special characteristics of telex which does not really need a conventional switched path through the switching network. Modern telex systems have also to provide for some data switching capabilities. System architectures in India for telex and data switching have been described explaining the design rationale behind each one of them. The first system was derived from the architecture of crossbar switching system but an autonomous unit was employed for bit coupling. Stored Program Control using specially-designed switching processor and character switching were introduced next. Followed by this, microprocessors were used to implement first the centralized and then the distributed control architecture for a modern telex and data switching system.

Stored Program Controlled Network: Data Base Administration System-Overall Description and Operational Characteristics

Large amounts of data about every customer line number and billing number in the country must be available for the Stored Program Controlled (SPC) Network features to operate. A method of obtaining, organizing, and cleansing the data or administering the necessary network data bases was needed. While much of the data could be obtained through each telephone company's service order system, these systems vary substantially in capabilities from one company to another and even from one region to another of the same company. To obtain the data, a new support system called the No. 2 Data Base Administration System (DBAS) was designed and new operational procedures for the telephone companies were developed. The DBAS interacts with all types of service order systems to obtain the data; provides initial load, as well as immediate and routine updates for the network data bases; and handles customer queries, statistics, special studies and other administrative functions off-line for the data bases. This minicomputer-based system bridges the gap between the telephone company paper flow and the SPC network. The DBAS provides reliable data in a timely fashion to the network to ensure the viability of the initial features. It provides a general capability for administration of additional customer data which may be required for future SPC network features.

Stored Program Controlled Network: NO. 1/1A ESS-SPC Network Capabilities and Signaling Architecture

The No. 1/1A Electronic Switching System (ESS) will play an important role in the evolving Stored Program Controlled (SPC) Network because, as a major electronic switching system for local and combined local/toll service, it provides direct interfaces to many of the Bell System's customers. It provides important capabilities required for System 800 Service and for a variety of other new SPC network services. This paper describes several of the basic SPC network capabilities provided by the No. 1/1A ESS. It also describes the architecture and implementation of its common-channel interoffice signaling (CCIS) subsystem, CCIS call-processing software, and System 800 software.

Stored Program Controlled Network: Prologue

The rapid introduction of electronic switching systems with Stored Program Control (SPC) has made possible the interconnection of the control processors by high-speed data links to provide common-channel interoffice signaling (CCIS). Not only does this permit higher-speed, lower-cost, more reliable setup of connections, but also the transfer of packets of information for more flexible call control. The papers in this issue describe the evolution of the SPC network concept since the introduction of CCIS in 1976 and the first new services which will exploit the power of this new network capability.

Stored Program Controlled Network: Calling Card Service-Overall Description and Operational Characteristics

Conventionally, operator assistance is required for most nonsent paid telephone calls (calls that are billed to a number other than the calling number). Examples of these calls include collect, credit card, and bill-to-third-number. These three types of calls currently represent about two-thirds of all operator-handled toll calls. To reduce the need for operator assistance, a new service, Calling Card Service, enables customers to make credit card calls by dialing in the billing information without the assistance of an operator; it also provides an alternative to operator-assisted collect and bill-to-third-number calls. This new capability is made possible through changes in the Traffic Service Position System (TSPS) No. 1, and uses the Stored Program Controlled (SPC) Network. By providing customers with an alternative to operator assistance, Calling Card Service is helping the Bell Operating Companies (BOCS) and independent telephone companies stabilize operator work force requirements. This paper gives a basic description of Calling Card Service and the customer interface. It also describes the implementation in TSPS, and other areas of the SPC network, and discusses some of the effects on telephone company operations.

Stored Program Controlled Network: Routing of Direct-Signaling Messages in the CCIS Network

This paper compares and contrasts the two methods currently used to route messages through the common-channel interoffice signaling (CCIS) network. Since its introduction in 1976, the CCIS network has been providing routing of telephone signaling messages between switching offices using permanent virtual circuits. In 1980, a new datagram routing capability, called direct signaling, has been added that significantly enhances the network's ability to interconnect Stored Program Control (SPC) systems. Stored program control systems interconnected by the signaling network can now communicate in support of improved SPC network services in addition to CCIS trunk-related call-control signaling. This paper briefly reviews banded telephone routing and then describes and compares direct signaling routing. The new flow control procedures required to implement direct signaling are discussed and two examples of applications using direct signaling are presented.

Stored Program Controlled Network: CCIS and SPC Network Performance

Common-channel interoffice signaling (CCIS) represents a major advance in interoffice signaling speed and capability over current inband signaling systems. The introduction of CCIS between Stored Program Control (SPC) switching offices is reducing ineffective machine attempts (IMAS) caused by transmission and switching irregularities associated with inband signaling. Because signaling between CCIS-equipped switching offices is concentrated in a relatively small number of signaling links and signal transfer points (STPS), a high standard of performance for the signaling network is essential. Therefore, the design of the signaling network incorporates many features to assure a high degree of availability. Cumulative data on STPS and studies of signaling links are the principal measures of signaling network performance. Data on their performance are presented that confirm the high availability of the signaling network.