4-wire Intercom module for building master stations with 6-- character (16 segment) alphanumeric display, electret microphone and red LED for operation indication. Prepared for connection of a loudspeaker, a keypad with 15 buttons, a handset and a switch for “privacy“. 2 inputs for floating contacts and 2 opencollector outputs. Instead of the internal microphone an external electret or noise-cancelling microphone can be connected.