Two or more control units combined in series can handle additional doors. Coded elements cannot be reprogrammed, making the actuators secure against manipulation. The control unit provides EDM (External Device Monitoring, also called MPCE Monitoring) and may be operated in manual or automatic start mode, which lets it function as a safetymonitoring relay. Misalignment tolerance of approximately a half-inch allows application on machine doors with a high level of vibration or alignment issues, and the 6-A/24-Vdc switching capability of the control unit allows connection directly to power contactors. The system works by passing an electromagnetic field from the switch to the actuator, which processes the signal and sends it back to the switch. It is then read by the control unit, which determines if it matches preprogrammed codes.