1. Wireless bidirectional call ringtone. (Industry first--focus)2. Empty working distance of 80 meters, floor 1 to 3 floor3. Working frequency 433MHz4. Nominal use5. Big button one-click call, easy operation for the elderlyLong working time, one charge can be about 40 daysBuilt-in lithium battery, battery capacity 600 mA, recyclableHigh volume, maximum volume 105dbVolume size can be adjusted, 5 gear adjustmentChangeable ringtone, 38 songsBlue light when calling/ringingLow power flash red light indicator, full power light indicatorDelivery of hanging rope, convenient for the elderlyHousing adopts plastic material, electroplating, gloss, high gradeSmall size: 79mmx42mmx13.5mmColor: SilverMaterial: plasticPackage Contents:2 * ButtonsOnly 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.