| 摘要 |
PURPOSE:To obtain excellent zoom function without using a compensating circuit to the high voltage fluctuation by switching the frequency ratio of a write clock and a read clock of a video signal to a storage circuit. CONSTITUTION:A video signal converted into a digital signal by an AD converter 11 is written in a memory 12 in the timing of the write clock fw and read from the memory 12 in the timing of a read clock fr. When an output of an n- value command circuit 51 is at an ''L'' level, the multiple (n) of a multiplier 16 is set to n=2, then the system is activated corresponding to the circuit operation of 1 field 525-line. When the output of the n-value command circuit 51 is at ''H'' level, since the (n) of the circuit 16 is set to n=1, the relation of f2=fr is obtained. A command is issued to a reset pulse generating circuit 18 at the same time and the reset pulse has a desired timing. A resistor 22 of a vertical oscillation circuit 2 is short-circuited by a transistor 23 at the same time and the vertical sweep width is changed. Then a part of the screen is magnified.
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