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8.5 NRS 90224 pilot tone & ground fault surveillance
The extension NRS 90224 is meant for insertion. It includes a 19 kHz tone generator and a selective 19 kHz
receiver with evaluation stage for pilot tone surveillance. Also incorporated is a monitoring circuit with fault storage
and display driver, to guard the cable network connected to the output.
8.5.1 Pilot tone surveillance:
Integration of the extension NRS 90224 provides continuous self-monitoring of the amplifier. This gets
accomplished in the way that an extremely low-level 19 kHz pilot tone signal is introduced to the signal path
following the input level control LEVEL. After passing the amplifier stages, the pilot tone signal is filtered out at the
output and the result is evaluated. If the measured signal declines the pilot tone's predetermined threshold at the
output or is not present at all, the READY indicator (7) dims and the READY fault message relay drops. When
using the INPUT MODULE NRS 90225, the fault message is output as collective fault message with the floating
contact of the READY fault message relay via the REMOTE CONTROL connector (16). When using the REMOTE
MODULE NRS 90222, error occurrence is monitored and output by the PROMATRIX manager DPM 4000 (for
further details, please refer to the PROMATRIX handbook).
8.5.2 Ground fault surveillance:
When installing and operating 100V-loudspeaker networks, compliance to the VDE regulation DIN VDE 0800 is
mandatory. Especially, if 100V-loudspeaker networks are included in alarm system applications, all security
standards have to be in accordance to the security class 3 standard.
When off-ground potential loudspeaker cable networks are employed we recommend insulation-monitoring using
the ground fault surveillance module NRS 90224. Error recognition: An occurring ground fault either signals that
one of the cables is damaged - which most likely point towards a total line interruption in the near future - or that
connections have been carried out erroneously which may lead to malfunctioning of the entire system. The fault
message GROUND FAULT (6) is also maintained with very short (>5 sec) ground faults, as long as the amplifier is
powered-on or a loaded battery is connected. The fault message is displayed via the red GROUND FAULT
indicator (6). In case of an inserted INPUT MODULE NRS 90225, it is also outputted as collective fault message
with the floating contact of the READY fault message relay via the REMOTE CONTROL connector (16). When
using the REMOTE MODULE NRS 90222, error occurrence is monitored and output by the PROMATRIX manager
DPM 4000 (for further details, please refer to the PROMATRIX handbook).
The installation has to be performed as follows (see figure 8 and/or figure 9):
Caution Before opening the appliance, make sure to disconnect the mains and/or battery power source!
- To open the appliance, the top panel has to be removed.
- The extension kit NRS 90224 has to be inserted with its component side to the left (from the front view) until it
clicks in place.
- Re-install the top plate of the enclosure.
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