paging and prosound rdl line level mixing amplifier three channel audio mixer combines up to three line level signals to a single line level ... ptt push to talk function to hands free automatic muting and audio signal sensing for autopoweron function sensitivity and release ... 24~33vdc 30ma ground referenced mcm part 555-st-vox1 only $98.87 audio/video self-gated preamplifier ·self gated operation ·led level