This specialized cathode-ray tube contains a metal target plate with a printed image rather than a photosensitive surface. When an electron beam scans the plate, it produces a fixed video signal of that specific graphic. Broadcasters historically used them to transmit station identification logos or calibration charts before the advent of digital pattern generators.
Heard on the job
The station relies on an old monoscope to broadcast the test pattern during off hours.
Insider tip
Unlike a standard camera tube, a monoscope cannot capture moving images from the outside world.