In case of an emergency, the alarm information can be sent to the host with just of the button Four level volume can be adjusted, 38 ringtones can be , the sound is crisp and loud Omnidirectional gain, good penetration After an unexpected power failure, the Settings are still the same after the restart, and there is no need to repeat the operation Multiple people use at the same time, ultra-user-friendly design different buttons set different ringtones Wireless frequency: 433MHz Wireless distance: 350 meters (no interference in open space) Transmitter size: 60 x 14mm Receiver size: 72 x 72 x 17mm Battery: 1000MAH lithium battery material: plastic Color as shown Package Contents: 1 x receiving host 1 x data cable 2 x Call button 1 x English instruction manual 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.