Glensound GS-FW018 Single Channel Four Wire Subrack With IFBFeatures Mains Powered 19 Inch 1RU Single 4 wire circuit Program audio input Front Panel Mic or External Mic Mic gain control Compressor limiter circuit for mic Front panel lever key for switched output 4 wire input transformer balanced Program input transformer balanced Input gain controls for 4 wire & program Front panel Loudspeaker Headphone Jack (breaks LS) Variable LS dim (when lever key switched) Audio presence LEDs indicate incoming audio 4