Motorola Corporation

Dean E Banwart

Michael W Frenzer

Thomas J McClaughry

In a secure communication system, a secure point-to-point communication may be accomplished in the following manner. A first communications unit receives a request from an operator for a point-to-point communication identifying at least one destination communication unit. In response, the first communication unit generates a private call key variable by modifying an encryption key variable through the use of a predetermined function. Identity of the encryption key variable and information pertaining to the predetermined function is transmitted by the first communication unit to the destination communication unit. Upon receiving the identity of the encryption key variable and information pertaining to the predetermined function, the destination communication unit generates the private call key variable. When the private call key variable has been determined by the first communication unit and the destination communication unit, both communication units can engage in the secure point-to-point communication.

Method for point-to-point communications within secure communication

An improved digital signal detector for indicating the presence of digital data used in a communication system. While attempting to detect valid data, the detector buffers an incoming signal in a first-in, first-out buffer and allows locally generated data, instead of the buffered signal, to be coupled to an output. After detecting valid data, the detector estimates where in the buffer valid data commenced and either releases data from that point or further delays the signal up to the maximum length of the buffer before releasing it to the output. The invention provides high sensitivity and rapid detection, reduces variation in detection time over previous methods, and allows locally generated data to be inserted into the signal path without loss of valid data. The invention would find application in digital systems that require detection at high bit-error-rates without losing valid data and without relying on a particular message format to assist detection or in systems that locally insert preamble sequences for synchronization and control.

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Elgin, IL, United States of America

Dean E Banwart