Importance

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Abstract

A system for transmitting status information from a first location to a remote second location includes a monitoring device at the first location for monitoring the state of a plurality of relays or other devices that are capable of being in either an active or inactive state. The monitoring device produces a digital signal representative of the state of the relays. A first memory storage device contains a table of digital codes arranged so that a unique code is associated in a predetermined manner with each relay in each state. A processor is provided for processing the digital signal from the monitoring device and for accessing the table to retrieve the code associated with the present state of each relay. The processor also produces a first signal indicative of a change of state of any relay from the inactive to the active state. A transmitter transmits the codes retrieved from the processor in a predetermined sequence. An interrupt device is included that interrupts the transmission sequence in the presence of the first signal to cause the immediate transmission of the code associated with the relay that has changed from the inactive to the active state. A receiver at the remote second location receives the transmitted codes and verifies their validity by comparing the received codes to a table of expected codes contained in a second memory storage device. If the code received is valid, a decoder determines the relay and state represented and formulates and outputs a control word representative of the state of the monitored relays. If the code is invalid, an alarm signal is generated that inhibits the output of a control word. Once an alarm signal is generated, it is maintained until a valid code is received for each of the monitored relays without the reception of an intervening invalid code. Preferably, the transmission and reception of the codes are accomplished under control of a digital computer operating under program control.

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First Claim