Most manufacturers produce strikes with or without integrated monitoring functionalities, which relay back the state of the strike via single point monitoring of the latch in the jaw of the strike or by dual monitoring of both the latch and solenoid operation.
These signals from the lock can be used by the access control panel and its management software to report events, including alarm events, should doors be forced open or held open too long. It’s also possible to use door state to drive CCTV monitoring, which delivers situational awareness to security operators.
Something to note is that for redundancy of door state monitoring on high security doors, consideration should be given to using a separate reed switch on the door/frame connected to an alarm input.
The most secure installations require monitoring of the solenoid as well as the latch. This is the only way to ensure that your door strike is in fact locked and that a rodent, or intruder has not eaten/cut the power cable and your solenoid has not burnt out.
Something else to think about is polarity. Fail open (power to lock) or fail secure (power to open) are features of the electric strike that will be site-dependant. For example, if the strikes are tied into the fire alarm system it’s likely that they will be required to fail open (fail unlocked) once power to the strike is removed. Under other circumstances the strike may be required to fail in the locked position requiring the use of a fail secure (power to open) strike.
This is where the electric strike comes into its own. While other forms of locking may be cheaper to install, the electric strike when set to fail secure provides the most secure access control solution. When used with a mortice lock that has selectable hub locking, the inside lever can be set to free egress when power fails, while still preventing entry and at least partially preserving the audit trail and access logs of people movement around a building.
Developments in electric locking include higher holding forces; rapid power-to-lock/power-to-open and changeover; more shallow overall depth reducing frame cut-outs and possible weakness; rebated face plates for timber doors; low current consumption; low heat generating solenoids; cast one-piece bodies; supplying templates to assist fitting; weather resistant models and extended warranties.
When it comes to standards, ANSI is an American standard and not generally used or adhered to in Australia. Here the standard profile for most door strikes is the Padde ES200/ES2000. All local strike suppliers refer to this ‘Australian Profile’, as it is commonly referred to. Quality manufacturers and their distributors will give guidance to help the installer make the right choices.
When it comes to electromagnetic locks, well-designed types will have a built-in Hall Effect sensor for monitoring the lock/unlock status of the locking device (LSS – lock status sensor), a built-in reed switch contact for monitoring the open/closed status of the door (DSS – door status sensor) and an anti-tamper fixing plate to avoid hostile attacks targeted on the dome-nut-fixing bolt of the armature plate.
Bob Graham says Lox Locking also offers a third monitoring feature, which was requested by ASIO T4 to be incorporated into the LOX ES20M monitored strike, an anti-tamper switch (ATS).
“A microswitch monitors the position of the strike within the door frames, such that an insider attacker attempting to tamper with the wiring behind the strike would be detected by the removal of the strike from the frame,” explains Graham. “The tamper circuit would be a 24 hour alarm circuit and tampering of the strike during building occupation would be detected.”
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