1. Full-duplex intercom, talk like a phone call 2. Call open distance measured 500 meters (theoretical distance) 3. The indoor unit can be moved to use, distribution of charging seat, after use, put on the charging seat charging 4. Two indoor units or three indoor units can be realized indoor machine call each other, call each other call, a key to automatically answer (the function in a tow more than one can be implemented, is the standard tow one, such as the need to add more indoor machines need to contact the seller two, in addition to additional money to buy the machine, please know!) 5. Slim appearance thickness of only 18mm, similar products on the market thickness of 22mm or more, hold in the hand with texture! Please note: There may be slight color difference or difference in the actual product, which does not affect the use, please don' mind, thank you! Intelligent humanized design, with intercom lights and power light display, at a glance. Battery capacity: 1000 mAh lithium battery Charging voltage: DC5V Operating temperature: -20 degrees - 55 degrees Working frequency: 430MHz--490MHz Color: Black Material: plastic Package Contents: 1 x Wireless Intercom kit 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.