Electronic Access Controls
Do you always need a door contact?
In most applications, the low cost door contact is the only supervisory element that protects the investment made to control access to a door. The door lock and card reader (or keypad) provide security and prevent unauthorized entry only when the door is closed and locked.
By means of a simple door contact, it is possible to monitor several door conditions such as: door forced open, door remains open, or left open too long after a valid access, door relocked by a schedule while still open, or a user was granted access but never actually entered (important for anti-passback applications).
Also, most locking devices are available with integrated supervisory contacts. For example, electric strikes can be ordered with a contact that supervises the position of the door latch. Electromagnetic locks can be supplied with a sensor that reports the presence of the door plate (door is closed and lock is energized). These contacts are generally used in addition to a regular door contact and can provide valuable tamper information for high security applications. These contacts are often wired in series with the door contact but also monitored separately.