780P or 1080I

If you are looking into buying, or already own an HD TV, you may hear the terms 480P, 780P, 1080I, or 1080P. What do they mean and what do they have to do with HDTV?
We recently bouhght an RCA 40 inch LCD TV, and all the letters and numbers got me wondering, so I did sopme research on it and this is what I found.

Your cable or satellite provider sends a digital signal broadcasting with higher resolution than traditional digital signals.  A higher resolution will have a sharper picture image. Digital resolution is sharper than analog, and HD is actually a high end digital resolution. The 480/780/1080 numbers all have to do with how the high-def signal is displayed on the TV screen.

HDTV broadcast systems are identified with three major parameters:
Frame Size, Scanning Method, and Frame Rate which are broken down as follows:
a. Frame size in pixels is defined as number of horizontal pixels × number of vertical pixels, for example 1280 × 720 or 1920 × 1080. Often the number of horizontal pixels is implied and thus omitted from text. So saying 720P or 1080I actually refers to the number of vertical pixels with the scanning method. 480P, 780P, 1080I refer to the following:
480P was used for early plasma TV, it is not considered high-definition, but it is considered enhanced definition television.
720P(1280H x 720V) pixels is compatible with the newer plasma and LCD TV's, while HDTV transmitts at a higher resolution rate of 1080(1920H x 1080V) pixels. Currently 1080 is the highest resolution transmitted. You would need to receive a high definition signal from your cable or satellite provider to take advantage of a HDTV higher resolution formatting. These TV's would be labeled 1080I.Only Blu-ray and High-def video game consoles can put out a resolution of 1080p, while the cable or satellite providers do send out HD resolution of 1080. HDTV's will determine if it is to be interlaced or progressive scanned to the screen. Thus 1080i is 1920 horizontal pixels by 1080 vertical pixels with an interlaced scanning system.

b. Scanning method is identified with the letter 'I' for interlaced scanning or 'P' for progressive scanning.
Interlaced scan refers to the electron gun at the back of the TV tube firing off the odd lines of the onscreen image, then during a second pass, it shoots out the even-numbered lines. This all occurs within 1/30th of a second
Progressive scan works in the same manner as a computer monitor. The TV writes one full frame of video from left to right across the screen every 1/60 of a second. Since the entire image is drawn at one time--as opposed to an interlaced image -a progressively scanned video image looks more stable than an interlaced one, however, it takes more bandwith to transmit and convert.

c. Frame rate is identified as number of video frames per second.
For interlaced systems an alternative form of specifying number of fields per second is often used.
For progressive systems, the resolution will be display with a frame rate of 24, 30 or 60.
1080p/24, means the same frame is displayed every 24th of a second.
1080p/30, means the same frame is displayed every 30th of a second.
1080p/60, means the same frame is displayed every 60th of a second.

An LCD TV may not always be a High definition TV. If you have high definition signal being broadcast to you home, but you have an LCD TV that is not HD ready, the TV would convert down the HD format resolution .