Features Outdoorbell is power supplied by 4pcs AAA battery (not included), easy to replace the battery. Indoorbell is used with an external USB data cable. Low power consumption, long standby time for outdoor bell up to 4 months. Big and adjustable speaker, clear voice, can be used as mobile interphone. Outdoor bell pair with indoor bell by learning its code, 1 outdoor bell can paired with 2 indoor bells and no interference each other. Specification Condition: 100% Brand New Item Type: Door Bell Material: ABS Plastic Color: As Pictures Shown Outdoor-Bell: Voltage Range: 4 x AAA batteries (not included) Working Temperature: -20-55 Transmission Distance: Approx. 200m / 656.2ft in the open, 5 - 50m / 16.4 - 164ft in obstacles Working Frequency: 467.