Abstract: A retrofit electromechanical door knob assembly is adapted to fit within an aperture in a door in place of a conventional mechanical lock assembly. The retrofit door knob assembly is similar in appearance to a conventional door handle assembly, but includes a motor coupled to a latch, and suitable electrical and mechanical key inserts for receiving separate electrical and mechanical keys. Either a mechanical or an electrical key can unlock the latch. The electrical key insert includes a data probe within the handle for receiving the electrical key and a means for gripping an electronic key to allow a user to turn the handle with the key after the latch is unlocked by the motor, thereby withdrawing the latch.