For TwinBus door intercom systems. Extra flat design. Optical call display / night design. Differentiation between door and floor calls. 5 melodic ring tones. Volume adjustable in 4 levels. Call mute switch. 1-man commissioning. Door opener button. Light switch function via switching device. Dimensions: 90x220x42 mm (WxHxD). Accessories: ==>Flush-mounted and hollow wall installation with flush-mounted frame 17320..