door on the egress side of the door automatically. History The first modern direct-pull electromagnetic lock was designed by Sumner "Irving" Saphirstein in 1969 for initial installation on doors at the Montreal Forum. Fire concerns by local authorities in locking the doors at the Forum prompted management to find a locking solution that would be safe during a fire incident. Saphirstein initially proposed to use a linear stack of door holders to work as an electromagnetic lock. These door holders were traditionally used to hold doors open, but in this application Saphirstein believed that they could be packaged and adapted to work as a fail-safe lock. After a successful prototype and installation at the Forum, Saphirstein continued evolving and improving the design and established the Locknetics company to develop accessories and control circuits for electromagnetic locks. Under difficult business conditions, Locknetics was later sold to the Ives Door Hardware company and later, resold to the Harrow company. Much later this division was then again sold to Ingersoll Rand Security Technologies in 1999. The division was recently closed in 2007 and transferred to other divisions within Ingersoll Rand Security. Employees that were associated with activities at Locknetics, went on to form other electromagnetic lock companies including the Dynalock Corporation. Saphirstein continued developing electromagnetic locking technologies at other companies he initiated including Dortronics (later purchased by Sag Harbor Industries), Delta Controls (first purchased by the Lori Lock Company and then later purchased by Hanchett Entry Systems) and Delt-Rex Door Controls, all of which were located in Connecticut. Other engineers also left these companies to form their own manufacturing firms in electronic locking, including Highpower Security Products LLC in Meriden, Connecticut. Many other firms in both the U.S., Canada, and throughout Asia were later established to create additional product offerings for the direct-pull electromagnetic lock. Principle The principle behind an electromagnetic lock is the use of electromagnetism to lock a door when energized. The holding force should be collinear with the load, and the lock and armature plate should be face-to-face to achieve optimal operation. Operation The magnetic lock relies upon some of the basic concepts of electromagnetism. Essentially it consists of an electromagnet attracting a conductor with a force large enough to prevent the door from being opened. In a more detailed examination, the device makes use of the fact that a current through one or more loops of wire (known as