A Transmission Control Unit for High-speed Computer-to-computer Communication

An integral part of a process control and testing system used in several IBM plants is the transmission control unit (TCU). This paper discusses the design of the TCU, which provides the communication link between as many as 512 satellite computers and a central computer. It uses a microprogrammed polling scheme to establish connection with the satellites that need service and it permits messages of unrestricted length to be transmitted in either direction at the rate of 2.5 × 10
⁶
bits/sec over coaxial cables. With the aid of noise suppression circuits, it operates in the electrically noisy factory environment at an error rate of less than 10
⁻⁸
.