1. Wireless bidirectional call ringtone. (Industry first--focus) 2. Empty working distance of 80 meters, floor 1 to 3 floor 3. Working frequency 433MHz 4. Nominal use 5. Big button one-click call, easy operation compatible with the elderly Long working time, one charge can be about 40 days Built-in lithium battery, battery capacity 600 mA, recyclable High volume, maximum volume 105db Volume size can be adjusted, 5 gear adjustment Changeable ringtone, 38 songs Blue light when calling/ringing Low power flash red light indicator, full power light indicator Delivery of hanging rope, convenient compatible with the elderly Housing adopts plastic material, electroplating, gloss, high grade Small size: 79mmx42mmx13.5mm Color: Silver Material: plastic Package Contents: 2 * Buttons 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.