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NRS 90 224
B 411
S 406
S 405
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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