Flexible Intercom System Design for Telemetry Sites and Other Test Environments

Abstract

Testing avionics and military equipment often requires extensive facilities and numerous operators working in concert. In many cases these facilities are mobile and can be set up at remote locations. In almost all situations the equipment is loud and makes communication between the operators difficult if not impossible. Furthermore, many sites must transmit, receive, relay, and record telemetry signals. To facilitate communication, most telemetry and test sites incorporate some form of intercom system. While intercom systems themselves are a not a new concept and are available in many forms, finding one that meets the requirements of the test community (at a reasonable cost) can be a significant challenge. Specifically, the test director must often communicate with several manned stations, aircraft, remote sites, and/or simultaneously record all or some of the audio traffic. Furthermore, it is often necessary to conference all or some of the channels (so that all those involved can fully follow the progress of the test). The needs can be so specialized that they often demand a very expensive "custom" solution. This paper describes the philosophy and design of a multi-channel intercom system specifically intended to support the needs of the telemetry and test community. It discusses in detail how to use state-of-the-art field programmable gate arrays, relatively inexpensive computers and digital signal processors, and some other new technologies to design a fully digital, completely non-blocking intercom system. The system described is radically different from conventional designs but is much more cost effective (thanks to recent developments in programmable logic, microprocessor performance, and serial/digital technologies). This paper presents, as an example, the conception and design of an actual system purchased by the US government.