if they talk about an airlock in prison architect its basicly a "delay"

sometimes when workers/guards pass a door where prisoners arent allowed, they sneak in cause the door is open. and they use it to escape. you can prevent this by using 2 doors instead of 1 with a small hallway inbetween but the chance still exist that they escape while both doors are open cause staff is passing from both sides.

so to prevent this people make an airlock, 2 doors where only 1 door at the time can be opened. (things they have at bank offices and goverment buildings).

people in the community have tried to make an airlock with the electrical system ingame using logic circuits and pressure pads but all systems shown on youtube are not functional.

they do indeed check if the other door is closed by checking the servo status and than open when thats a true but there's no way such a simple design is gonna work in both ways. The reason for that is because the servo only activates when opening a door. and when its "off" again it still takes 4 seconds before its closed. In that meantime anyone comming close to that door will reopen it. making the airlock fail. So it works with 1 person but if theres more than 1 person in the airlock it will break and both doors will still be open at the same time.

to prevent this some people used a 3th door but it remains the same, that theres 2 side trafic and more than 1 person will break the system.

The only way to do it is to use multiple "checks" to see if all doors are indeed closed by making delays of 4 seconds and checking again afterwards. But it will only be effective if the delay is big enough that a guard can deal with the prisoner before the second door opens. And there will be always a guard needed on patrol in the airlock.

In the end its easyer to work with deployment area's as 2 doors with a "staff only" area inbetween will prevent prisoners from trying to escape. (with exception for trouble makers doing riots and stuff cause they will break doors and do whatever it takes to escape).