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A100K10370
SPA-V2 Public Address & General Alarm System
Installation & Configuration Manual
4 Appendix A: Local Mute
Local mute is used for instances where feedback is caused by close
proximity between a PA panel and a loudspeaker.
To prevent the feedback loop from occurring when making a PA call, the
local speaker or speaker loop is disconnected.
Under normal circumstances, the speaker loop is connected via a relay
box that defaults to a closed loop to the affected speaker(s).
The PA panel has a local mute output that is connected to the coil of the
relay. This triggers when only this panel is activated, giving an active
24VDC out, which breaks the audio going to the local speaker(s). Local
mute outputs are limited to 50mA. Our recommended relay box, IRR-
3 V1, consumes ~20mA, leaving 30mA for power loss in cable used.
We estimate a maximum of 10 meters based on the average 0.75mm
2
power loss.
If you are using a different relay, maximum cable length must be
calculated based on cable specifications and remaining current
available after relay consumption.
L
Warning: Do not exceed 50mA for the cable and relay as this will cause the
system to become unstable.
Figure 16 Alarm/Mic Panel with Local Mute for Dual System
