The indoor unit and outdoor unit are wirelessly connected at a long distance without wiring. The open distance can be up to 200 meters, and the obstacle distance is 20-50 meters. Two-way intercom, wireless distance 200m. The loudspeaker is loud, the volume is adjustable, and the ringtone is changed, the intercom sound quality is clear, and it can be used for mobile intercom. Scope of application: residential buildings, factories, hotels, hospitals, tea houses, shops, and places in Ligong. Working frequency: 467.6375MHZ Working temperature: -20--55 degrees Celsius Working frequency: 467.6375MHZ (no waterproof function) Power supply voltage 1.5 (V) Power supply mode External machine: 4 AAA batteries + internal machine: USB cable power supply (without battery) The outdoor machine has a long working time, 4 batteries can reach more than half a year Product weight: 105g Scope of application: residential buildings, factories, hotels, hospitals, tea houses, shops, and public places Colour: black Material: ABS Size: 10x6x1.3cm Package Contents: 1 * Doorbell 1 * Receiver Only the above package content, other products are not included. Note: Light 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.