Delay lines in TV sets

While the subject of delay lines has been hashed out here for a while, most of the delay lines used in TV sets are probably not too reasonable for data storage. In particular those used in NTSC sets are to balance the delays in the chroma circuits (those that are on the 3.579 sub carrier) with the luma signal (which isn't processed). Since the chroma goes thru additional circuits, the other signal needs to be delayed (not very long) to maintain the registration. In PAL sets, I believe that the same idea is used. The difference is that in PAL sets a different subcarrier frequency is used, and the demodulation products are different for every other line (they swap In-phase, and Quadrature). SECAM is a bit different, as they do NOT use in-phase and quadrature (simultaneous) demodulation of the color difference signals, but alternate them line by line (The 'S' in SECAM). This necessitates a one line delay to keep around the other color difference signal to display on the line. More complexity in the receiver with all that switching and "storing", and while it has lower color resolution is more immune to phase differences which plague signal chains in I & Q (NTSC/PAL) systems. PAL systems on the other hand with the swapping of I & Q every other line (the 'A' in PAL) usually nulls out the differences. If you decide to make up a delay line to hold CPU data, try a prototype using shift registers. They are a bit easier to make up, and often the chips are available. The problem is that they come in weird (at times) sizes (132, 80, and the like). I'll leave it to the reader to determine the usability of odd sizes and their original use. -- Sorry, No signature at the moment. ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs