AE-OPT-412 is suitable for all AE series multi-function clock/timers and elapsed timers with two, three, four, five or six digit configurations. When the elapsed timer reaches its preset value on count up, or zero on count down, the timer will reset and start over. On AE series models with built-in controls, the preset values and the start and reset functions can be controlled locally. On models that do not have the built-in controls, the preset values must be set at the factory. Also, a single dry contact closure is required to start the elapsed timer at the desired instant.