To prevent accidental lock-in of operators often a safety padlock is used. The ALPHA makes the use of a safety key mandatory. Door Closed
The ALPHA interlock blocking device prevents opening an access door until the unique coded key is turned and extracted. The ALPHA then block the door from closing and in doing so switching the safety contact of the door switch until the safety key is returned in the lock Door Open
The ALPHA ensures the door can only be opened when the safety key is removed. As long as the operator is present in the safeguarded area (with the safety key), the door cannot close and the machine cannot restart.