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

Abstract

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.