Multiple songs Music ringtones, volume adjustment. Press to generate electricity, no battery required, strong signal, long distance. Easy to install and use. Home security. Energy saving and environmental protection. Super loud wireless doorbell, a homemade smart wireless doorbell, (simple installation without battery) Installation details: Take out the product and plug the indoor unit into the power outlet. Pay attention to whether the blue indicator light of the bell guide decoration on the indoor unit is flashing. If the blue light flashes on the indoor unit, the indoor unit is working normally; Press the call button on the outdoor unit transmitter to check whether the indoor unit rings the doorbell normally. During the test, the indoor unit will ring the doorbell normally, indicating that the product is working normally.