NEIEP Mechanics Practice Exam

What is meant by self-holding a call relay?

1. Keeping a relay engaged through external control

2. Holding a relay in with its own contact

3. Automatically releasing the relay after a period

4. Switching the relay off when a condition is met

The correct answer is: Holding a relay in with its own contact

Self-holding a call relay refers to a mechanism where the relay maintains its own contact closure after being initially energized. This is accomplished through a configuration where the output of the relay is fed back to its own coil, allowing it to stay engaged without requiring continuous external power. Once the relay is activated, it closes its contacts, which in turn keeps power flowing to its own coil, resulting in a maintained state even if the originating control signal is removed. This principle is commonly used in various electrical systems to ensure that once the relay has been activated (for example, by pressing a button), it remains in the 'on' position until an additional action is taken to disengage it. Understanding this concept is crucial as it provides insight into how relays can be used to control circuits in various applications, especially in automation and control systems.