This interlock is very simple to operate. As the chamber is pressurised, the interlock mechanically locks the bolt in the extended position. The interlock bolt cannot be retracted until the chamber pressure is less than 1psi.

When the bolt is in the retracted position the gas supply to the chamber is isolated and the chamber cannot be pressurised.

When the bolt is retracted the chamber is vented through the interlock vent ports, this ensures that the chamber cannot be pressurised from another source. This facility also allows the interlock to be used in a vent only configuration, in which case port B would be plugged.