Abstract: Video input circuits are disclosed for a video hard copy controller of the type that converts and formats video signals into digital signals for application to a hard copy generating device. The video input circuits comprise a video amplifier circuit having input terminals for receiving a composite video signal comprised of a video data component and a synchronization component, control terminals for receiving a gain control signal to control the gain of the amplifier circuit, and output terminals at which an amplified composite video signal is developed. An automatic gain control circuit is coupled in feedback relation between the output and control terminals of the amplifier circuit for generating the gain control signal to control the gain of the video amplifier such that, in said amplified composite video signal, the potential difference between first and second portions of the synchronization component thereof substantially constant.

Abstract: A video hard copy controller includes first means for receiving serial input video signals from a first source. Second means is coupled to the first means for converting the serial input video signals into a first set of parallel digital signals. Third means is coupled to the second means for receiving the first set of parallel digital signals. The third means includes means for receiving a second set of parallel digital signals from a second source and means responsive to a control signal for selecting between the first and second sets of parallel digital signals for output to a hard copy generating device in order to produce a hard copy fascimile of the images represented by the selected set of parallel digital video signals.

Abstract: An automatic gain control circuit for controlling the gain of a video amplifier of the type adapted to amplify a composite video signal comprised of a video data component and a synchronization component. The circuit comprises first means coupled to the output of the video amplifier for sampling the voltage level of the amplified composite video signal during a first portion (e.g. backporch) of the synchronization component. Second means is coupled to the output of the video amplifier for sampling the voltage level of the amplified composite video signal during a second portion (e.g. tip) of the synchronization component. Third means is coupled to the first and second means for comparing the actual potential difference between the sampled first and second portions with a predetermined reference potential and for generating a gain control signal representative of such comparison.

Abstract: Video data detect circuits are provided for a video hard copy controller of the type that converts and formats a video signal into a digital signal for application to a hard copy generating device. The video signal includes a video data component and a synchronization component including horizontal synchronization (HS) periods. The video hard copy controller includes means for generating sample clock pulses at a frequency proportional to the HS periods. The video data detect circuits comprise first means for generating a predetermined video threshold reference signal; second means coupled to the first means and responsive to the video signal and to the predetermined reference signal for generating a binary signal at one state for so long as the voltage level of the video signal exceeds that of the predetermined reference signal and at another state for so long as the voltage level of the video signal is less than that of the predetermined reference signal.