| 摘要 |
The AC mains voltage (Uw) is monitored. The required DC supply voltages (U1, U2) are derived from this via corresponding rectifier circuits (GA1, GA2). Two timers (R1, R2, C1 or R3, R4, C2) are provided, the first of which generates a reset potential for the process-control circuit (microprocessor) in the event of an interruption of the AC mains voltage if this interruption lasts longer than the time span which can be pre-defined with the timer. The second timer is activated when the voltage is restored and generates output information after a pre-defined time span with which the process-control circuit is released. It thus begins to execute the pre-defined programs with the start-up address taken in on the basis of the reset potential. If the device represents a small dial-up PBX system, the generated reset signal and its de-activation are able to ensure, for example, that no relays are erroneously activated in the event of mains voltage activation, failure or restoration. This is important if a so-called door-opener relay (T1) is present. <IMAGE>
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