Accepts balanced or unbalanced electret microphones with 6.35mm (1/4") jack plugs . Part of C-TEC's patented 'Outreach Plate' audio input extension system (see key features section below for details). Compatible with C-TEC's entire range of PDA102, 200E, Pro-Range and ML1 induction loop amplifiers. Can be connected to any third-party audio or induction loop amplifier using an APV 24V 250mA power supply. Mounts on a 25mm standard UK single gang back box.