| 摘要 |
A signaling system for detecting at a central station a message from a remote location at which one or more different messages can be generated. A coded signal is generated at the remote location and an "error" uniquely determined by the message to be transmitted is inserted into the coded signal and the altered signal transmitted. A receiver at the central station is arranged to detect the presence of such inserted "error" so as to correctly identify the message that has been transmitted, whereby such message can be displayed or used to activate an alarm device.
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