Monoscope

The monoscope was similar in construction to a CRT, with an electron gun at one end and at the other, a metal target screen with an image formed on it.

The reflected electrons were picked up by an internal electrode ring, producing a varying electrical signal which was amplified to become the video output of the tube.

For example, the classic Indian Head test card as used by many television stations in North America, was often produced using a monoscope.

Monoscopes were available with a wide variety of standard patterns and messages, and could be ordered with a custom image such as a station logo.

Monoscopes were used as character generators for text mode video rendering in computer displays for a short time in the 1960s.