| 摘要 |
A digital dissolver dissolves between two different video signals in synchronism with a composite sync signal. Frame pulses are separated from the composite sync signal and are used to generate a high frequency signal in phase locked relation with the frame pulses. The high frequency signal is fed to a programmable frequency divider under the control of gating and control circuitry to provide an output pulse in response to each occurrence of a selected number of cycles of the high frequency signal, the selected number being a function of the selected dissolve rate programmed into the divider by thumbwheel switches or by signals from a remote location. The pulses are fed to a binary counter which feeds a digital to analog converter to generate a dissolve signal of generally ramp-like waveform. The dissolve signal and its complement are applied to a pair of multipliers to attenuate the two different video signals.
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