Schlage 740 Series emergency break glass products are designed for use as an emergency release of doors not normally used for daily ingress/egress. These may include laboratories, testing areas or other similar work rooms. It is also used in fail safe, multiple door interlocks and perimeter protection systems that involve the central control and potential lockdown of electronic locking devices, as an on-site emergency release. A “break glass” solution may be preferred in many situations over a conventional "pull box" installation because it is less vulnerable to misuse or tamper actuation.
The 740 Series emergency break glass units consist of a replacement break glass cartridge that normally holds the plunger-activated switch depressed until the cartridge lens is broken. When the lens is broken, the plunger moves forward and alters the switch contact position.