When installing electric strikes and maglocks, don't forget to install the surge suppression devices, especially if they are included with the lock. Many people doing installs make this common omission that causes technical support calls and premature equipment failure. They make think that these devices are optional. Included diodes, MOVs or TransZorbs (TVS) act as surge suppressors that prevent high voltage spikes from radiating to other electrical components. A strike is an inductive load (coil of wire) internally, and when they are allowed to de-energize rapidly (when a controlling relay cuts power) the strike briefly acts as a source of voltage. This voltage can be much higher (>1000V) than the voltage that was originally supplied to energize the strike (12V or 24V). The higher voltage is generated by a rapidly collapsing electric field in the solenoid of the strike. You want to clamp this voltage (keep it at a low level <40V). Unclamped, this brief high voltage spike can radiate to the access control and other low voltage systems causing electrical malfunctions and damage. These spikes cause large arcs that can very quickly destroy contacts of relay outputs and even vaporize processors and other sensitive components found in electronic door control hardware. Varistors are not polarity sensitive, but diodes are, so note the details in your strike installation manual. Also, change these devices out after a few years. Reference standard BHMA A156.31 for specifications in this area when installing access control systems.