1, the air damping type time relay, also known as bellows type time relay, it is based on the air compression resistance to delay, its structure is simple, cheap, wide time delay range (0.4 ~ 180 s), but the delay precision is low.

2, electromagnetic relay time delay time is short (0.3 ~ 1.6 s), but its structure is simple, usually used in delay occasions and dc power.

3, the principle of dynamic time relay like clocks and watches, it is obtained by internal motor drive gear rotation and time delay. The relay delay of high precision, wide time delay range (0.4 ~ 72 h), but the structure is more complex, the price is very expensive.

4, the transistor type time relay, also known as electronic time relay, it is to use time delay circuit for time delay. This kind of relay with high precision, small volume.