Audio speaker unit for Simplebus system, complete with terminal block and digital audio management system with Eco-cancelling, watertight loudspeaker and electret microphone, loudspeaker volume can be adjusted from the front. Complete with microprocessor and DIP SWITCH with 8 positions for programming calls to users. 33Vdc power supply via special power supply unit art. 1595. On-board electronic lock-release function (3A), plus C, NC, NO 10A relay contacts. For use in modules Art. 33400, 33401 and 33402. Dimensions: 4"x2.2"x1.5". Compatible with all SBTOP functions and products. Allows call addressing for up to 120000 users. Timed lock-release input and door open indication.