On Distributed Communications Series

VIII. The Multiplexing Station


In this Memorandum, the operations of and the equipment in the Multiplexing Station of the Distributed Adaptive Message Block Network are examined and described.

The Multiplexing Station feeds the Switching Nodes (described in Vol. VII in the series), and constitutes the interface between the users and the network; it might be likened to a telephone central office. Each station is able to accept a mixture of start-stop teletype signals; 600-, 2400-, 9600-, 19,200-bit/sec synchronous signals; and a limited number of highly intermittent megabit/sec signal subscribers. It is able to simultaneously process traffic from a maximum of 1024 separate users, connected into any single Switching Node.

The system possesses flexibility for automatic rerouting of calls to the most recent location of a subscriber; it uses push-button dialing, contains automatic self-synchronizing end-to-end cryptographic protection, and is suitable for both digital voice and digital data applications. Additionally, all buffering operations necessary to package and unpack data streams from network users are performed at the Multiplexing Station. Transmission is automatically suppressed when no active data is being transmitted between connected users, allowing highly efficient use of the network in handling secure digital voice data.

The Multiplexing Station is comprised of a magnetic drum, a magnetic core store, and necessary special-purpose transistorized digital processing equipment, occupying about 150 cu ft.

In addition to detailed descriptions of the components and the operations of the Station, some engineering specifications, flow charts, and computational criteria are included. Some conclusions regarding feasibilities, and areas requiring more detailed investigation, are contained in the last two sections.