| 摘要 |
<p>Radio alarm systems with a multiplicity of channels for transmitting messages between glass break detector, break detector (opening detector) and the like, and a microprocessor-controlled central unit are known. The individual channels are formed in this case in accordance with the time-division multiplex system or by using the frequency-division multiplex system. In order to increase interference immunity in a simple manner and to allow at the same time the interference-free transmission of messages via the different channels, the channels are formed in the transmission direction from the detectors (sensors) to the central unit by using frequency hopping. The spread (expanded) channels thus formed are subsequently superposed on one another and converted to a single carrier frequency. <IMAGE></p> |
