| 摘要 |
<p>With the circuit arrangement, the double line frequency which is used as the reference quantity for picture auxiliary signals can be derived from a colour TV signal according to the CCIR PAL standard by coupling the colour carrier frequency with the horizontal frequency via a so-called quarter-line offset, and by using a signal derived from the colour carrier by frequency division and multiplication. The signal (2f<!>H) derived from the colour carrier (F) is fed to the trigger input (A) of a monostable multi-vibrator (15). The vertical frequency (fV), which is divided in the ratio 2:1, is fed directly to the control inputs (J, H) of the multi-vibrator (15), as a 25Hz exponential voltage, via a pulse former (12), an integration stage (13) and a time-specifying resistor (14). On the other hand, it is fed to the control inputs with the interposition of a capacitor (16). The time-specifying resistor (14) and capacitor (16) are dimensioned so that exactly double the line frequency (2fH), in the form of the positive or negative edges of the output pulses (c) of the monostable multi-vibrator (15), is available at the output (Q, Q) of the monostable multi-vibrator (15), under the influence of the vertical frequency (fV) and the frequency (2f<!>H) which is fed to the trigger input (A) of the monostable multi-vibrator (15), and which differs from the double line frequency (2fH). <IMAGE></p> |
