What will disturb the operation of a vertical interval switcher?
Vertical Interval Switchers rely on incoming sync detection. Usually, the sync signals are stripped from input #1, and are used to operate (after some processing) the switching circuitry. If the switcher is microprocessor or RS-232 controlled, then the Vertical generated signals are also used by the microprocessor. When a low quality video source is connected to input #1, such as a satellite relayed video source or even a VCR in STOP or PAUSE mode, the switcher receives a very noisy signal or only noise. In most cases, this noise disturbs the normal operation of the built-in sync stripper, generating erroneous Vertical signals that might disturb or even completely block the operation of the switcher. In order to avoid this problem, the simplest procedure is to connect a good source to input #1 or, as in many video studios, the master studio Black Burst source.
