12v external wired doorbell. Dingdong ring for access control. No battery required 12V four wire doorbell retardant, high temperature resistant, oxidation resistant, corrosion resistant, environment-friendly and recyclable The doorbell is and pleasant with chip, good effect and stable use. After the product is connected to the access control system, press the doorbell button of the access control machine to make a pleasant ding sound. Power supply voltage: 12 (V) color:White Material:ABS Package Contents: 1 x 12V Wired Ding Doorbell Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.