Abstract: An adjustable safety interlock is disclosed for microwave ovens or other high voltage electrical apparatus. The interlock is actuated by the movement of a counterbalance arm when the door is opened. The amount of movement necessary to actuate the interlock is altered by changing the position of the interlock switch relative to the counterbalance arm. The interlock switch is pivotally mounted on the side of the apparatus for this purpose. Pivotal movement of the interlock towards and away from the counterbalance arm is achieved by a finely threaded bolt. The bolt is biased in the direction of greater safety by a compression spring. The interlock is readily accessible during production and thereafter only by authorized personnel.