Interlocking Doors

Doors that interlock work together so only one door may be open at a time.

Switches are placed on the door so the power supply knows when a door is open.  These switches are called Door Position Switches.

Air Lock

An example of an air lock application would be a clean room.  The main point of concern is not security but air.  The air is constantly filtered and cannot be contaminated with outside air.

Both doors are normally closed (they have door closers) and unlocked.

When a person opens the first door, the power supply immediately locks the second door.

The person then enters the chamber and allows the first door to close.  Once that door closes all the way, the power supply will unlock the second door.

A time delay may also be used to properly filter the chamber before allowing either door to open.

From the perspective of the power supply here's what is happening behind the scenes.  At it's resting state both doors are unlocked.  Should one door open, the power supply immediately locks both doors.  It then unlocks both doors once it detects both doors are closed.

As complicated as this all sounds, it is really a very simple system.

Door position switches are mounted to the door.  The power supply monitors these switches to know when to lock and unlock the doors.

Man Trap

A man trap application is designed to keep someone from moving through both doors quickly.  A robber or fleeing prisoner needs to be slowed down as much as possible.  Furthermore, the doors contain access control devices so only authorized personnel may pass through the doors.

Both doors are normally locked.

A key is required to pass.

The trick is to require a key on either side of both doors.  Regardless of which direction people are moving they must use a key to pass.  This requires 4 key locks, one for each side of each door.

The power supply requires a timer.  Once a door is opened the timer ensures the door locks again after a preset time (6 seconds for example).

From the perspective of the power supply here's what is happening behind the scenes.  At it's resting state both doors are locked.  As one door is unlocked using a key, the timer begins it's count down.  When it reaches zero that door locks again.

The critical factor is that an opened door completely shuts out use of the other door.

Once both doors are closed, either door may be unlocked by using the key.

The system is called a man trap because once a person is between the two locked doors they are trapped. The only way out is by use of a key.

Key switches are often used in these applications, but a card swipe, keypad or access device works equally well.

Regardless of the switch type used, 4 units are required.  One for each side of each door.