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An electric strike is a latching mechanism that operates electrically to secure or release the extended latch or bolt of a mechanical lock or exit device. When an electric strike releases the latching mechanism, the lock/device remains locked. The electric strike's keeper releases, opening a path that permits the extended latch or bolt to exit the electric strike, permitting the door to be swung open. The keeper either remains released until after the latch or bolt re-enters the electric strike or, in the case of electric strike' designed for retractable latches, the keeper closes and the latch retracts over the keeper as the door closes.
An electric strike takes the place of the strikeplate for a mechanical lock. There are electric strikes designed to operate cylindrical locks, mortise locks, deadbolts, and exit devices. There are electric strikes designed to be installed into wood, aluminum, and/or metal jambs.
The components of an electric strike are the faceplate, keeper, lip, body, and locking/unlocking mechanism. The faceplate is used to attach the electric strike onto the door jamb. The keeper is the breakaway portion of the electric strike, which opens to release the latch/bolt, and closes once the latch/bolt re-enters the electric strike securing the door. Most electric strike keepers hinge against the body along the lip. The body attaches to or is part of the faceplate, which contains the electrical components, the keeper and the lip.
All electric strikes have an opening designed to contain the latch or bolt. The length and depth of this opening varies depending upon the specific model of electric strike. Some electric strikes are designed to accommodate a 1/2” throw cylindrical lock latch. Other electric strikes are designed to accommodate up to a 1 inch deadbolt. In addition, specialty electric strikes are designed to accommodate the Pullman bolt of a rim design exit device. Some models of electric strikes have the capability of operating with more than one lock configuration.
All electric strikes operate similarly. Just about every electric strike operates using a solenoid or coil. For our purposes, we will discuss the solenoid-equipped electric strikes. A solenoid is comprised of a plunger (movable armature) surrounded by a coil of wire. When the coil of wire is electrified, it becomes a magnetic field that moves the solenoid in a prescribed direction for a specific distance. In this condition, the keeper is either secured or released. When power is removed, the plunger moves back into the original position, and the keeper in the opposite condition.
There are two types of solenoids: the intermittent duty solenoid and the continuous duty. The intermittent duty solenoid is designed to be powered sporadically, just to release the door for someone to gain access. Most intermittent duty electric strikes are Fail-Secure, requiring power only to release the keeper and open the door. Continuous duty electric strikes are designed to be powered constantly and can function as Fail-Safe or Fail-Secure.
In the recent history of electric strikes, the heavy-duty electric strikes were equipped with external solenoids. These solenoids could be about three-quarters of an inch in diameter and extend out of the electric strike body approximately three to four inches. There was a choice of the solenoid position — extending up, out, or down. As electronics evolved, many solenoids were moved into the bodies of the electric strikes.
Electric strike solenoids are usually operated by low voltage electrical power sources, such as transformer or power supply. They are usually 12 or 24 volts, AC or DC or convertible. A convertible electric strike can be configured to operate as either AC or DC. The operational difference between a AC and a DC electric strike is the DC electric strike is just about silent when operating. Whereas, an AC electric strike buzzes when powered. An AC electric strike uses a DC solenoid with an attached full wave bridge rectifier. The full wave bridge rectifier converts the AC to DC current. If you do not need this buzzing sound, consider a DC electric strike.
The Folger Adam product line, marketed by HES, Inc, continues to offer high quality industrial grade electric strikes to satisfy a variety of needs for extra heavy duty durability and tamper...