Emergency Stop Switch 

The Emergency Stop Switch, also known as E-stop switch, emergency switch, kill switch, or emergency button is a fail-safe control switch that provides safety for the system and for the person using the system. The emergency stop switch must be highly visible in color, label (CP-132) and shape to operate easily in emergency situations. So the button must be red mushroom head with symbol of arrow, EMERGENCY or STOP. It needs a twist to release electrical contacts to allow system restart.