| 摘要 |
A transmitter has a plurality of parallel inputs, and each input is connected to a switch. The transmitter receives a trigger signal that has a constant frequency. Using the trigger signal, the transmitter provides a signal which consists of individual series signals, each one of the series signals representing the status of one of the switches. The series signal also includes a sync signal which precedes the series signals associated with the status of the switches. These series signals are generated in synchronism with the trigger signal that is applied to the transmitter. A receiver receives the series signals and also the trigger signal. The sync signal is detected in the receiver, and a status signal is generated in response to each of the series signals following the sync signal as those signals are received. Each status signal is applied to an input which is identified by the number of repetitions made by the trigger signal after the sync signal is detected. An alarm may be activated in response to the status signal on the receiver outputs, the number of which equals the number of inputs on the transmitter.
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