Deadbolt
Also known as deadlock, a steel latch approximately one inch long, which exits the edge of the door and passes into the door jamb near the keyhole. In this way a deadbolt is distinct from a spring-bolt because a deadbolt cannot be moved to the open position except by turning the cylinder. A deadbolt can either be a single cylinder or a double cylinder. A single cylinder will use a key on one side of the lock and can be operated by a twist of a knob on the other side. A double cylinder lock will use a key on both sides, so there is no knob. A deadbolt is often used as part of a home security system because it makes a door more resistant to entry without the correct key. .

Deadlock
Also known as a deadbolt. See deadbolt definition.

Digital video monitoring
Used with a CCTV security system. The monitor allows you to view the output from several cameras at the same time.

Door alarm
A loud warning signal is produced when the alarm is opened, triggered or shut. Once the alarm is triggered a signal is sent to alert the user, home security monitoring center and/or police to a specific danger. The alarm can be wireless. Wireless door alarms may operate with batteries which need to be replaced, or they may be plugged in or wired to the wall.

Door and window contact
A protective device that can send a notification to a compatible home security system when the opening and closure of doors and windows occurs. There are three different styles typically used by many alarm companies; a recessed contact, surface mount contact and roller-ball contact. A recessed contact is hidden in the window track or door jam. A surface mount contact works much the same as a recessed however it is visible when the door or window is closed. A roller boll contact is in the hinge side of a door jam. The spring-leaded ball is pushed in when the door is closed.