Features 1、INTELLIGENT AND LASTING: Mobile intercom, internal machine has constant power, outside machine has long working time, intelligent pairing combination 2、ADJUSTABLE VOLUME: 15 chords ring tone, three levels of volume adjustment, the internal machine can be connected to each other, very safe 3、TRANSMISSION DISTANCE: 200Meter long distance effective transmission, easily through four walls, the receiver with flashing light reminder function 4、EFFECTIVE WATERPROOF: The waterproof design of the launcher complies with IP44 waterproof standard and effectively prevents the intrusion of rainwater 5、APPLICATION SCENARIO: Wireless voice intercom doorbell is widely used in home, office, laboratory environment, medical treatment, etc. Specification Item Type: Wireless Voice Intercom Doorbell Material: ABS Battery: Internal Machine: 1 x Rechargeable lithium battery 3.7V 890mAh(built in) External Machine: 3 x 1.5V AA battery(not include) Application: Widely used in home, office, laboratory environment, medical and so on Basic Parameters: Radio Frequency: Approx. 410M - 490M Package List 1 x Internal Machine 1 x External Machine 1 x USB Cable 1 x Screwdriver 1 x User Manual