A pulse-code-modulated telemetry decommutator-computer interface

A hardware interface was developed which connects an existing pulse-code-modulation (PCM) decommutator with computer input/output (I/O) channels. The interface was designed to operate with a number of existing computers with the proper interconnecting cable configuration.

In addition to electronic interface functions, the interface also provides a means for editing incoming telemetry data and a first-in-first-out (FIFO) buffer memory. Editing makes it possible to pass only selected PCM data values from the PCM decommutator output data. Editing in conjunction with FIFO memory allows the processing of data at telemetry data rates higher than otherwise possible. The FIFO memory minimizes data rate constraints imposed by computer processing time overhead and synchronizes telemetry data flow into the computer.

A prototype was fabricated using wire-wrap modules and was checked out on a Modcomp Model MCII computer. The prototype was later connected to a Digital Equipment Corporation Model PDP 11/40 computer. Printed circuit modules were fabricated and installed in the final operational system. The system was put into use in test data acquisition.