integrated bell button wiring, metal bell buttons with gold-plated and maintenance-free button contacts, long-lasting nameplate lighting through LEDs, long-lasting nameplate cover made of 5 mm thick plastic glass, nameplate size 41 x 15 mm, any bell button can be used as a light switch button, light symbols included, control tone for the visitor when the bell button is pressed, very easy assembly and installation, temperature range: -20 degrees C to +50 degrees C, with microphone, loudspeaker and electronics for easy connection to the TCS:BUS, good voice quality, volume and microphone sensitivity adjustable, prepared for the connection of further bell button extensions, color: natural anodized aluminum, dimensions: 223 x 135 x 20 mm