Importance

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Abstract

Disclosed herein is a system and method of serially transferring a sequence of data bits between a computer and a portable information device such as the Timex Data Link.TM. watch, using the CRT of the computer as a transmission medium. The computer is programmed to display sequential display frames on a frame-scanning graphics display device and to illuminate line segments within the display frames to represent individual data bits. Each line segment has a continuous length on the display device which produces an optical pulse of a corresponding duration. Each data bit is encoded as a different line segment length to produce an optical pulse for each data bit having a duration which is dependent on the value of the data bit. For example, a pulse representing a binary value of 0 has a duration which is relatively longer than that of a pulse representing a binary 1. A receiving device monitors the optical signal created by the CRT and detects rising signal edges. It interprets each rising edge as the beginning of a single bit. After detecting a rising edge, the receiving device waits for a pre-determined time and then samples the optical signal. If the pulse from the CRT is still present, the receiving device interprets the data bit as a binary 0. Otherwise, the receiving device interprets the data bit as a binary 1.

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First Claim