Abstract: Video control signals are received at a video input port of a system. A determination is made whether the video control signals are valid or invalid. When video control signals represent a valid video signal, providing a delayed representation of a control signal to a synchronization input of a display engine of the system, and when the video control signals represent an invalid video signal, providing a an alternative signal to the synchronization input of the display engine.

Abstract: An incoming pulse train is evaluated for interpulse spacing and pulse repetition rate by first shaping the pulses into a desired configuration in a dial pulse shaper (12). The shaped pulses are applied to a pulse counter and controller (14) to generate numerator and denominator signals of a divide function. The numerator and denominator signals are gated through a data selector (16) to an up counter controller (24). The up counter controller (24) gates a 2 KHz clock to a counter in a divider and display (18) during the denominator signal and during the numerator signal the counter within the divider display (18) is gated to perform the divide functions. The divider and display (18) carries out a division function of the numerator by the denominator with the quotient representing the percent interpulse interval or the pulse repetition rate depending on the mode of operation.