Features: Self-powered doorbell that requires no battery. Wireless range up to 150 meters (in open area). 4 volume levels between 0 – 110 DB (can be set to mute). 51 ringtones: Easily maintained and fixed. Self-generating button, no battery is needed. IP44 waterproof ,Long time placed in the rain recommended to buy waterproof cover, otherwise affect life. 150 meters receiving distance: The receiving distance may be affected by the environment and obstacles. 4 volume levels between 0 – 110 DB (can be set to mute). The receiver flashes when the button is pressed and then followed by a melody 51 ringtones to choose from). Learning function: Hold the volume key for 5 seconds to pair and then quickly press the button several times to signal pairing success. Intelligent power management. power supply:ac110-240v 50/60hz. Specification: Transmitter size: 75 x 45 x 18 mm. Receiver size: 100 x 66 x 30 mm. Reminders: 1. The button cannot be placed on an iron door because it will interfere with the signal. 2. Works in heavy raining, however we recommend buying a waterproof cover for long-term use. Otherwise, the life expectancy will be shortened. Package includeds: 1/2 x Receiver. 1/2 x Transmitter. 1 x Installation Kit. 1 x User Manual