Function module of the AMI series, number of bell buttons: for up to 16, mounting type: flush-mounted, material/color: aluminum, anodized silver, connection of bell button module: via 4-pin service plug, voice transmission: full duplex (for indoor stations with handset), voice output volume: adjustable, acknowledgement tone volume: adjustable, system configuration memory: interchangeable, light switch function: on customer-provided bell button, speech connection during door standby time: adjustable, microphone: integrated and detachable, door opening function extension: on R terminal, number of wires: 3-wire required, technology: 2-wire TCS:BUS, current consumption, at rest: 5.9 mA, current consumption, maximum: 13.5 mA, clear dimensions HxW mm: 82x82, external dimensions HxWxD mm: 105x105x28, permissible ambient temperature: -20 to +50 degrees C, The TCS:BUS speech module can only be combined with bell button modules and/or the LCD graphic display module, 3 buttons. The loudspeaker module is used for outdoor stations with the LCD graphic display module. All other modules can be freely combined