Abstract: A theft protection system for an electrical instrument includes a metal jacket power cord having an enlarged plug at each end. The base of a first locking device is secured to the instrument and one end of the cord is plugged into a socket on the instrument. Thereafter, a cover is placed over the plug and socket and is locked to the base with the cord passing through a slotted opening in the cover. A second base member in the form of a plate is secured to a standard duplex electrical outlet. The plug at the other end of the cord is inserted into the electrical socket and is then covered by a cover member which is locked to the base plate. The cord cannot be removed from the wall outlet or the instrument without unlocking the cover members.