Final answer:
Programmed timers change their output state when the accumulated time matches the preset value, initiating or halting connected devices or signals in control systems.
Step-by-step explanation:
Programmed timers' output contacts change state when the accumulated time equals the preset value. Timers are common components in various control and automation applications such as PLC (Programmable Logic Controller) programming or even in simpler electronic circuits. When a timer is set with a preset time value, it begins to accumulate time once triggered. Once the accumulated time reaches the preset threshold, the output contacts of the timer will switch from their normal state, either to open or close a circuit, thereby starting or stopping a connected device or signal.