Door Position Switches are used to monitor the status of a door or to provide an initiate signal to Securitron®'s XDT delayed exit logic timers and DPA door prop logic timers. The components require drilling a 3/4" [19mm] diameter hole in the door and frame directly opposite one another. The large magnet is needed to overcome the shielding effect of a steel door (where aplicable). The DPS is a Normally Closed switch (SPST). The distance depends on the door type and gap between the door and frame but is in the 1/2"-3/4" [12-18mm] range. Includes a magnetic switch and a cylindrical permanent magnet.