Zung Sung Enterprise Co., Ltd.

Time delay relays are simply control relays with a time delay built in. 

Their purpose is to control an event based on time.

The difference between relays and time delay relays is when the output contacts open and close: 

on a control relay, it happens when voltage is applied and removed from the coil; on time delay relays, 

the contacts will open or close before or after a pre-selected, timed interval.