What s the difference between a test card and a tuning signal?
That s easy! A test card is used for detailed adjustment of receivers, i.e. for testing, and incorporates detailed geometrical patterns to allow checks to be made. Many broadcasters still transmit test cards, at least for periods of the day. Tuning signals are not seen nowadays; they were simple visual devices allowing viewers to tune in their set and check picture balance without detailed technical complications. The most technical thing you saw in a tuning signal was a greyscale (black and white tuning signals) or coloured blocks and a picture incorporating flesh tones (colour tuning signals).
