Abstract: A motion tracking system includes a processor, a heat source generator operatively coupled to the processor, and a heat sensor operatively coupled to the processor. As the system moves along a surface, the heat source generator generates a heated area on the surface. The heat sensor senses the heated area on the surface, and the processor determines the movement of the heat sensor relative to the surface based on the heated area. The processor in one mode determines the relative direction of movement by comparing the location of a pulsed heated area relative to a reference location. In another mode, the processor determines the relative direction by comparing the location of a thermal dissipative zone to the location of a hot zone of a continuously heated area.

Abstract: A two-way video telephone station includes a television screen for displaying an image transmitted by a distant party to a telephone conversation, a video camera for electronically photographing a human subject and periodically transmitting his picture to the distant party, and position-indicating apparatus for keeping the subject within the camera's field of view. The position-indicating apparatus includes a pair of light-emitting diodes (LEDs)--one on each side of the camera. The LEDs are visible to the subject when he is out, or almost out, of the camera's field of view. Because the LEDs can only be seen when the subject needs to take corrective action, they act as passive restraints that are completely unnoticed when the subject is properly positioned. Red LEDs are used to indicate that movement should stop if the subject wishes to be centered in the picture transmitted to the distant party.