| 摘要 |
PURPOSE:To prevent malfunction, by automatically switching an output into a reference signal oscillated inside the device, if an external synchronizing signal is incoming. CONSTITUTION:If no external video signal is incoming at input terminals 1, 1', a vertical synchronizing signal is not obtained from an NOR gate 7 and the output is at ''L'' always. Thus, a transistor TR8 is kept at a cut-off state and an NOR gate 12 is at inhibit state. Then, since the output of the NOR gate 12 is at ''L'' independently of ON/OFF of an electronic edition switch 13, an NOR gate 16 is at ''release'' state and an NOR gate 18 is at ''inhibition'' state. After the reference signal of a reference signal oscillator 20 is amplified at a TR21, it is outputted via the NOR gates 16, 19. |
