Features Versatile Application: Ideal for schools or factories, this timer switch provides a reliable solution for bell ringing, enhancing al efficiency and convenience Easy Installation: Featuring a guide rail mounting design, this timer relay simplifies the setup process, allowing quick and hassle- installation in any environment Customizable Timing: Set the bell ringing duration from 1s to 99s, giving you complete control over your schedule and ensuring timing for your needs Features: 1、The timer switch can be used for school bell or factory bell. 2、Guide rail mounting design is convenient for installation. 3、The bell ringing time can be set from 1s to 99s. 4、Low error,only 1s/day error in working,and the minimum setting time is 1min. 5、With a built-in button cell ML621 which dose not require replacement. Specification: Item Type:Timer Switch Minimum Setting Time: 1min Working Voltage: 220V 50/60Hz Timing Error: ≤1s/D Rated Operating Current: AC-15 220V 3A Thermally Stable Current Value: 16A Ringing Time: 1s~99s Installation Method: Rail Type Built-In Battery: Rechargeable Button Battery ML621, No Need to Replace Package List: 1 x Timer Switch 1 x English Users Manual Package List 1 x Timer Switch 1 x English Users Manual