Mains Voltage Door Chime with Built-in Transformer. Mechanical Door Chime. Maximum recommended circuit length 15 metres. Bell push and bell wire sold separately - this listing is for the chime only. Door Chime with built in Transformer. Requires mains wiring to transformer position. Traditional "ding dong" sound. Can be used with illuminated (lit) bell pushes if required. Dimensions: 105mm wide x 170mm high x 45mm deep.