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  The Green Bank Telescope (GBT) is a collection of mechanical and electrical subsystems, that, taken together, form a radio telescope. The coordination and control of these subsystems is accomplished using the GBT Monitor and Control (M&C) system, a hierarchical distributed system consisting of software modules running on multiple computers communicating over a local area network (LAN). The M&C system is implemented using general purpose computers as well as specially designed hardware. The system is designed to minimize real-time communications and timing dependencies between subsystems. This allows the non-deterministic Ethernet protocol to be used successfully for control purposes and for data transport. The whole system is synchronized via a combination of Network Time Protocol (NTP) [1], InterRange Instrumentation Group B (IRIG-B) and 1 Pulse Per Second (1PPS) signals distributed by the site timing center.

John Ford
Fri Mar 13 16:06:38 EST 1998