The board allow to add a spare amplifier unit in the DXT 7000 system. The LT 7208 override voltage output is used to activate the AC 7212 relay in case of the main amplifier is faulty and switch the spare amplifier output to the respective loudspeaker line. AC 7212 terminal shall be directly connected to a pair of LT 7208 loudspeaker 50-70-100 V outputs. The spare amplifier audio input is to be connected to either the MU 7100 system bus override audio out (when the spare amplifier serves the entire system) or the MU 7100 local bus override audio out (when the spare amplifier is for a single MU 7100 only).