1、User-friendly, simple design, no need to ask for professionals or installers' help, completely free of renovation costs. 2、Multi-purpose.The receiver also has an ultrasonic mosquito repellent function. 3、With constant voltage circuit design, it has high efficiency and energy saving effect, effectively increasing the service life by more than 50%. 4、The doorbell consumes less than 3W, and the transmitter uses a 12V volt 23A battery. 5、It has a wide range of uses, not only regarded as a general doorbell, but also be used for special purposes such as contact, paging, patient care, and emergency notification. Features: User-friendly, simple design, no need to ask for professionals or installers' help, completely free of renovation costs. Multi-purpose.The receiver also has an ultrasonic mosquito repellent function. With constant voltage circuit design, it has high efficiency and energy saving effect, effectively increasing the service life by more than 50%. The doorbell consumes less than 3W, and the transmitter uses a 12V volt 23A battery. There are factors affecting the use of the doorbell as follows:electromagnetic interference, installation on a closed iron door, shielding, weather and humidity, and no timely replacement of the battery. It has a wide range of uses, not only regarded as a general doorbell, but also be used for special purposes such as contact, paging, patient care, and emergency notification. Specification: Condition: 100% Brand New Material: ABS Color: As Shows in Pictures Transmitter: 72*40*16mm / 2.83*1.57*0.63in Receiver: 96*61*26mm / 3.78*2.4*1.02in Power supply for transmitter: 23A 12V(Battery included) Power supply for receiver: 2*1.5V(Not included) Weight: 178g Package List: 2* Receiver 1* Transmitter Notice: Please allow 1-3cm error due to manual measurement and make sure you do not mind before ordering. Please understand that colors may exist chromatic aberration as the different placement of pictures.