F51 F52 doorbell button
F51:CR2032 Lithum Cell
F52:23A 12V Battery
It can’t work alone ,work with M521 ,M525, M557 Doorbell and KERUI Alarm System.
Ring the bell outside the door.
Ring the bell the doorbell host in the back door will emit music.
Act as an alarm
When a person is at home, uncomfortable, and contact tools such as mobile phones are not nearby, the doorbell button and doorbell act as alarms to make sounds and attract attention.
F52 waterproof button
This one is more suitable for outdoor installation.