The Model 303 can operate in 2 different timing modes: In the On Delay Mode: When power is applied to the coil, the timer will delay for the preset time before energizing the relay. The relay will remain energized as long as power is applied. Power must be removed to reset the timer. In the Interval Mode: When power is applied to the coil, the relay will energize immediately and remain energized for the preset time period. At the end of the time period, the relay will de-energize and remain de-energized until power is removed from the coil. Removing and re-applying power will restart the timer, energizing the relay. An SG version of this model is available using silver with gold flash contacts.

The Model 303 is UL Recognized and CSA Certified.