المخطط الصندوقي لنظام بال ذو التأخير (pal-d) .. كتاب التلفزيون الملون والعادي

9-20 Block diagram of the PAL-D system:

In this system there is a time delay line

(64 microseconds), which is the time of one line
It is similar to the SECAM system but more accurate - the coloration signal is given to the delay line as it is given directly to the collector and subtractor circuit. Their results are given to the detector (R-Y) and its symbol (7) and to the detector (B,Y) and its symbol (U). They are connected to the signal of the basic oscillator with a sub-frequency of color - so the detector (U) is fed directly from the oscillator. The detector (7) is fed through the page shift circuit Figure (17-20) and (18-20) and from the sum of the delay line, the collector and the subtractor, we get at the output of the detector (U) the average signal (B-Y) for lines (1) and (1) (2) - And we get the signal of the detector (7) and from its output an average (R-Y) of the lines (1) and (2) - also - and the same work is repeated for the signal of line (3) and the signal behind the line (2).The signal of the two detectors is always the average of the signal Two lines The existence of the reflective switch is necessary because the signal (7) reflects its polarity in the second line for every two lines, and its signal is always positive by means of the reflective switch.

20-10 Hannover lines:

These lines appear in the form of an effect on the color when the phase progresses, as a result of deficiencies or lack of alignment in the line delay circuits - in the PALD delay system, as well as from some page difference errors in transmission. In the PAL system, distortions appear in the form of an error in saturation, while in the NTSC system, these errors appear in the form of distortion in colors. This has a greater effect and disadvantage, and the presence of a phase control between the sub-carrier frequency generator and the detector reduces the page error and reduces the effects of Hanover. In the case of the delayed PAL system, the error is corrected electronically before the detection process, by adding color information to the pairs of scan lines The resultant of the direct and delayed color signal represents the average value of the B- signal on two lines A page changer is placed on one of the direct paths before the collector circuit and the subtraction process takes place and produces the average value of the signal (R-Y) on the two lines and the page is changed at the rate of the horizontal line - thus the two signal components are separated Color and feeding each of them to the special detector without the color errors found in the simple PAL system.The effect of Hanover is canceled except when there is a malfunction, especially the amplitude imbalance for both the direct and the delayed signal.The amplitude balance is done in a circuit (balance matrix).