Abstract: A method for establishing a secure communications link between first and second terminals includes a step of exchanging a first message. The first message contains information describing encryption devices and communications modes available within the terminals and user authentication information. The method also includes a step of selecting, in at least one terminal, a common key generation and ciphering algorithm. The method further includes steps of exchanging a second message for providing data to form traffic keys, exchanging a third message for synchronizing secure communications and initiating secure communication.

Abstract: An apparatus and method for adjusting set clearance altitude of an aircraft to control the aircraft to fly along a predetermined path relative to the terrain below. A terrain following radar system and a stored terrain elevation data base are used to determine the respective positions and elevations of selected portions of the terrain downrange from the aircraft. This information is used along with pre-stored information relating to the ability of a ground threat to detect the aircraft and the roughness of the terrain to compute three different altitudes. The first altitude (Ia) represents the maximum height at which the aircraft can fly without being detected by the ground threat. The second altitude (Da) represents the maximum desired altitude of the aircraft at any time during a flight. The third altitude (Ra) represents the minimum altitude at which the aircraft is allowed to fly.

Abstract: A compact, miniature instrument for providing biofeedback information of interest to a user. The instrument is comprised of a wrist-watch size unit, which includes a temperature sensor for sensing the user's external skin temperature and a finger-mountable unit, which includes a heart beat sensor for sensing the user's heart beat. Processing circuitry is provided for computing various biofeedback parameters of interest to the user, including pulse rate, time rate of change in pulse rate and time rate of change in external skin temperature. Timekeeping circuitry is provided for keeping track of various time-related parameters, such as time of day and calendar date. A display is provided for selectively displaying biofeedback and time-related information to the user.

Abstract: A body-mounted measuring instrument senses the heart beat and inner body temperature of a user. The instrument includes a computing circuit and a timekeeping circuit for calculating elapsed time, total heart beats, pulse rate, and difference in body temperature from a predetermined normal temperature. A display is included for indicating various physiological parameters measured and an alarm system warns the user if an excessive heart rate and/or body temperature condition occurs. The instrument is well-suited for an athlete engaged in activities such as running, swimming and bicycling, not only as a safety device to warn the user of the occurrence of a dangerous condition, but also as a distance measuring and velocity computing device. The instrument computes distance travelled by the athlete during an exercise period based on the total number of heart beats and the increase in body temperature occurring during the exercise period.