Timer trippers help define the exact switching points in a compatible mechanical timer schedule, and this Intermatic T-100 Series set includes 1 on and 1 off tripper using the 156T1978A reference. Trippers are useful because they are the small but necessary hardware pieces that physically trigger the timer dial mechanism to switch the load.This part has practical value because replacing missing or worn trippers can bring a mechanical timer back into dependable service without replacing the whole timer mechanism. A properly selected Intermatic tripper set helps preserve intended schedule function and contributes to more accurate automatic control.This type of part is especially useful when the original trippers are lost, damaged, stripped, or no longer engaging the timer dial correctly. That helps restore scheduled switching with a simple, direct service part.Installed in the proper application, this tripper set helps support dependable timer performance and more confident long-term scheduling accuracy. Intermatic T-100 Series tripper set with 1 on and 1 off tripper Helps define switching points in compatible mechanical timers Useful when replacing lost or worn original trippers Supports dependable automatic on and off scheduling Improves timer accuracy and service confidence