10 Years Ago
School security was the cover focus for March 2013, and Jerry Levine wrote about global school lockdown options with networked locks. Ingersoll Rand (now Allegion) contributed an article on school lockdowns using the Schlage AD-400- wireless locks. In an article titled “Improving Your School’s Security In An Emergency: What You Can Do Now,” ASSA ABLOY’s Christopher Gaugan recommended that schools control and monitor their entries and enable classrooms to be secured quickly from the inside with the aid of specially designed lockset functions. Much of the advice is still valid today. Tim O’Leary wrote about the expandable aptiQ multi-credential reader capable of handling magnetic stripe, proximity and smart card applications. Jerry Levine reported on the C9100 and C9200 mailbox locks introduced by CompX to satisfy new United States Postal Service regulations. These five-pin tumbler mailbox locks have five depths of cut. Gale Johnson previewed new wireless security products. O’Leary checked out the Qvis entry level video surveillance kit for locksmiths just entering the CCTV market.
20 Years Ago
A Locksmith Ledger editorial examined a New York Times article about the vulnerability of master key systems. Jerry Levine reported on the Alarm Lock PDL3000 Prox Lock. Dick Zunkel discovered the wonderful world of power transfer devices. Tim O’Leary explained how to program access control systems. Several pages were devoted to specific instructions for programming various electronic locks, which is important information when you are asked to program a lock you have never seen before. Levine used a Trimco adaptor for a retrofit installation of a Sargent cylindrical lever lock in place of an old unit lock. Levine also reported on the Audi/Porsche/VW sidewinder keys. Ledger also showed ways to measure with dial calipers. Gale Johnson stated the case against master keying. Richard Formica had some suggestions for sight-reading wafer locks. Tiny fit keys to a GM Hummer. Writer Steve Kaufman offered his opinions on the "Future of Locksmithing," still very interesting reading 20 years later. Tiny offered suggestions on servicing hand-change safe locks.
Guide To Electromagnetic Locks
Editor’s Note: Though some of the product models in this article may have been discontinued, the basic overview of electromagnetic locks is still helpful today.
Electromagnetic "mag" locks provide a fail-safe locking mechanism, which requires power to maintain the holding force. For most applications, they secure a door for the purpose of traffic control. The mag lock is placed either onto or into the doorjamb, usually along the header.
An electromagnetic lock provides its greatest holding force when the door must pull away from the magnet. For a swing type door, the mag lock is placed adjacent to the lock edge of the door, requiring the door face to be pulled directly away. For a sliding door, the mag lock is placed on the locking leg of the doorframe. When the door is closed, the edge contacts the mag lock. To open, the door must be pulled directly away from the magnet.
The magnetic portion of the conventional electromagnetic lock is made up of many "E"-shaped thin ferrous metal plates placed adjacent to each other, creating a wide "E". Lying on their back, they form the three metal lines on the face of the magnet. The size and the number of the "E" shaped plates partially determine the holding force of the electromagnetic lock. A copper wire winding creates the magnet field that results from the flow of Direct Current (DC). Electronics are installed to complete the circuitry.
All components are placed into a housing. A non-ferrous potting mixture fills the cavity and encapsulates the components. When the mixture hardens, the surface is machined flat to ensure maximum holding force. Most electromagnetic locks' ferrous metal surfaces are then plated to protect against corrosion and increase durability. Some mag locks have a separate compartment for the wire connections and circuitry.
A ferrous metal strike plate or armature assembly slightly larger than the surface area of the electromagnet completes the locking mechanism. When powered, this spring-loaded plate is drawn flush against the electromagnet. The oversized strike plate provides sufficient surface area if there is settling or wear, protects against tampering and can resist removal of the mounting screws.
For commercial and institutional applications, mag locks are normally 12-24VDC powered electromagnets. The amperage draw ranges from approximately 125mA to more than 500mA at 24VDC, and 230mA to more than 600mA at 12VDC. The magnet size, holding force and construction determine the draw. The low amperage draw makes a simple single-door system capable of being operated by a .5Amp plug-in power supply.
Electromagnetic locks have been developed to incorporate just about every configuration of swing and sliding doors, including gates. Mag locks are available for top and side mount applications. They will have mounting holes in the face for rear mount. For top mount electromagnetic locks, there are two options: holes through the body of the magnet or an adjustable mounting bracket. For double-door applications, two electromagnetic locks can be installed into an aluminum housing, providing a cleaner and more secure installation.
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