The ST-GSP1 is a gated speech preamplifier designed to be used in a variety of situations where it is desired to produce an automatically switched line-level signal from a microphone. This module may be used in conjunction with other RDL modules to configure automatic mixing systems or may be used alone as a voice-operated module. The open-collector slave output may be used to trigger other equipment or RDL modules. The versatility of ST-GSP1 applications range from complete automatic mixing system design to the addition of automatic mic gating to the inputs of conventional mixers or amplifiers. The MIC INPUT may be wired for balanced or unbalanced operation. A phantom voltage terminal is provided for use with condenser microphones. The phantom input accepts dc voltages up to 48 Vdc and is internally filtered. The mic input gain adjustment has sufficient range to accommodate a wide range of microphones, from low-output dynamic microphones to higher-output condensers.