My dad built one of Lancaster's TV Typewriters back in the '70s for a black & white TV studio system. It was a huge improvement in speed and correctibility for

My dad built one of Lancaster's TV Typewriters back in the '70s for a black & white TV studio system. It was a huge improvement in speed and correctibility for static onscreen text overlayed on the video output, when previously it was done with physical hardware and chroma key using white letters on a black background.