| 摘要 |
PURPOSE:To miniaturize the constitution and to attain economy by selecting a frequency dividing ratio in a modulator for a CATV or the like and using a changeover switch so as to select a desired channel. CONSTITUTION:A reference signal frequency divider 18 is constituted by the cascade connection of a frequency dividing stage of frequency dividing ratio N3 (1/256) and a frequency dividing stage of frequency dividing ratio N2 (1/8). Moreover, a video carrier frequency divider 24 is constituted with the 1st stage of frequency dividing ratio 1/64 and the 2nd stage whose frequency dividing ratio is switched by a changeover switch SW2 so that the frequency dividing ratio of the 2nd stage is switched into 1/2173 and 1/2205. Furthermore, a frequency division output Fs has the identical frequency to that of a frequency division output Fr2 of the frequency divider 18 by setting a frequency dividing ratio N4 of an intecarrier frequency divider 24 to 1/176. Thus, the PAL system two-channel changeover is sttained by switching the frequency dividing ratio of the frequency divider 24 by using the changeover swithc SW2. |
