Large-Capacity Magnetic-Drum Memory System for an Electronic Switching System

A stored program-controlled electronic switching system (ESS) requires a large-capacity memory to store various kinds of programs and data. This paper describes a hierarchy arrangement including a high-speed memory and a low-cost largecapacity magnetic-drum memory for reduction of the cost of the ESS. The paper also describes the design philosophy, reliability, structure, and evaluation of the system. A magnetic drum with hydrodynamic floating heads (memory capacity: bits, clock rate: 2.2 MHz) was employed. The magnetic-drum memory system can provide transfer of individual words (each consisting of 41 bits), transfer of variable-length data by flag bit control, and content-addressable access. Furthermore, the system is designed to be most suitable for transfer of the large amount of data required by the switching system. The data throughput of the magnetic-drum memory system is 210 kbytes/s in a burst mode. The mean time between failures (MTBF) of the system is approximately h. This system assures reliability required for the ESS and high performance for application of the ESS to stored data switching as well as telephone switching.