Preset fixed interval (fixed cycle) reminder
——According to the preset length of time, three versions are provided for different applications. The cycle is based on the number of days, hours, or minutes, namely TR810S-xxxD, TR810S-xxxH Or TR810T-xxxM. When the countdown time is up, the 4 digits on the LCD screen will continue to flash and beep. For the convenience of application, two key operations are provided: one key and two keys.