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NRS 90 224
S 406
S 405
B 411
figure 9
printed board assembly 84175 in the DPA 4140 showing the NRS 90224 pilot tone & ground fault
surveillance and the bridges B411 and S405, S406 for switching the output voltage; inserted
Checking the pilot tone surveillance function:
When the NRS 90224 is installed and the power amplifier is switched on, the green READY indicator (7) has to light.
The testing and reset button TEST (3) serves as a function control for the pilot tone surveillance. With the TEST button
being engaged, the 19 kHz generator is inactive. The green READY indicator is off and the READY fault message
relay drops. Approximately 3 seconds after releasing the TEST button, the indicator has to light again. This method
can also be used to check system configurations with average-switching.
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