The interlock panel handles two independent interlock loops. One loop opens or closes the laser head internal safety shutters. This laser interlock loop interrupts the laser amplifiers and stops the lasers completely.
The second loop opens or closes the compressed air shutter (CAS). This propagation shutter keeps the lasers alive, but no laser light will leave the laser box.
The propagation shutter is also called compressed air shutter (CAS), what just means that it is operated with compressed air. In the technical documentation this term is often used and is synonymous with propagation shutter.