Abstract: A secure lock box system for secure storage and retrieval of a stored key includes a key fob device that requests access to a lock box by inductive or optical communication. The individual key fob is authorized for access to the lock box by prior radio communication with a key fob controller that validates the key fob. A lock box controller in combination with applied pressure to a latch hook conserves power and controls access to the key by operation of a low power solenoid and a latch mechanism. Tampering with the lock box is detected by a piezo film motion sensor that provides a signal to a microprocessor, which is awakened from a low power condition by the signal. Upon access grant or an unauthorized attempt at access to the lock box, a message is transmitted from the lock box to an annunciator. The annunciator relays a message concerning the attempted access to a server where a log is created and stored.

Abstract: The present invention is directed to an inversion scrambler and unscrambler having pseudo-randomly controlled polarity-reversing switches to invert and re-invert, respectively, an audio signal so as to restrict the intelligent dissemination of the audio signal. To improve security of the scrambled signal, the audio signal is concealed prior to scrambling. Concealment includes clamping the original audio signal to a predetermined value and optionally offsetting this clamped signal prior to scrambling. The concealed signal is scrambled by inverting contiguous portions of the signal at pseudo-random intervals, accomplished by a polarity-reversing switching network controlled by a pseudo-random code generator. Upon unscrambling, artifacts will appear at the inversion points of the unscrambling signal, due to bandwidth limitations inherent in any transmission path.