| 摘要 |
This invention relates to circuitry for extending TTL signals from a computer to a remotely located monitor and keyboard and which uses a first signal conditioning circuit proximate the computer to generally reduce amplitude of the video signals and bias them to a selected potential, after which the signals are applied to discrete conductors of an extended cable. The cable, in three embodiments described herein, may be up to 250 feet, 400 feet, or 1,000 feet. A second signal conditioning circuit at the monitor and keyboard end of the cable receives the attenuated signals and utilizes a threshold or pair of thresholds to effect reconstruction of the video signals prior to inputting them to the monitor. Significantly, amplitude reduction or attenuation of the video signals generally reduces high frequency video noise appearing on the keyboard clock conductor of the cable, preventing keyboard errors. Additionally, line capacitance and inductance in conductors of the extended cables is utilized to further attenuate the video signals.
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