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Configuring the Amplifier Chassis
Description, Installation, Operations, and Maintenance Manual
Federal Signal www.fedsig.com
8.6 ISMT Operations (Optional)
Intelligent Speaker Monitoring and Tapping (ISMT) requires special ISMT capable
speakers and a P-ISMT-G card in the Amplifier Chassis.
Remove the four jumpers on the right side of the front motherboard of the chassis
containing the ISMT card. Jumpers in all other shelves must be either on the right side or
removed altogether.
One ISMT card not only supports all four amplifier cards of its own chassis, but also all
other chassis sharing the standby cable connections.
It is a method of monitoring remote speaker status, using special communication
commands sent over the speaker lines. Through this communication link, you can
instruct each ISMT loudspeaker to change its tapping, recalibrate itself, and return status
information back to the ISMT card.
The ISMT card performs the monitoring procedure, when amplifier cards are idle, and the
system has allocated the time for the procedure.
During that time, ISMT card provides 24 Vdc power over the speaker lines for the
speaker monitoring circuits.
In one part of the procedure, a 20 kHz test tone is generated by the ISMT card, while
each ISMT speaker measures the current through its speaker coil.