Hikvision AX PRO Wireless Internal Sounder 

868 MHz two-way wireless communication
Configurable arming/disarming prompt sound and LED indicator
3 years battery life span (triggered every two weeks and alerting 90 sec for each triggering)
AES-128 encryption
Front and rear panel tamper-proof
3 kinds of alarm sounds: fire alarm, panic alarm, and intrusion alarm
Buzzer Decibel: 90 to 110 dB
Fully remote configurable through APP
Multiple enrollment methods and easy installation design
Frequency hopping against jamming for reliable transmission