Monoscope "cameras" were widely used to produce test cards, station logos, special signals for test purposes and standard announcements like "Please stand by" and "normal service will be resumed....". They had many advantages over using a live camera pointed at a card; an expensive camera was not tied up, they were always ready, and were never misframed or out of focus. Indeed, monoscopes were often used to calibrate the live cameras, by comparing the monoscope image and the live camera image of the same test pattern.