04 Can I use my TV as a monitor?
Description
This article is from the comp.sys.ibm.pc.hardware.video Frequently Asked Questions, by Michael Scott with numerous contributions by others. (v1.0).
04 Can I use my TV as a monitor?
Monitor prices are constantly dropping, but not as fast as many people would like. A nice 17+ inch monitor is still $800 or more. It would be nice if a cheap 20 or 27 inch television could be used instead.
Well, there are products available which will convert a VGA signal to one that is compatible with your television set. Below, I will outline the limitations that this type of setup has compared to a proper computer monitor. This may or may not be a viable option for you depending on what types of applications you use most frequently.
To understand what is and isn't possible, we need to know the differences between a computer's video signal and the one expected by your television (usually NTSC (North America) or PAL (Europe)). Typically, PC's display in one of 320x200, 320x240, 640x480, 800x600, 1024x768, 1280x1024 or 1600x1200. The lowest three pixel addressabilities are supported by VGA, and are the most common video modes used for VGA (often called DOS) games. The higher resolutions are typically used when in windowing environments like Windows 3.1, OS/2, Win95 or X-Windows. In addition, computers refresh the screen at varying rates, ranging from 50 to 75 or more Hertz (cycles/s). Most newer monitors support non-interlaced video at all or all but the highest pixel addressabilities. The digital signal is converted into an analog one that the computer monitor understands. If the signal is within the capabilities of the monitor, it will be displayed as a screen image.
Televisions are also analog devices, like computer monitors, but they are designed to accept a broadcast television signal like NTSC or PAL. The NTSC standard supports a maximum of 525 lines, while PAL supports up to 625. The screen refresh rates are fixed for NTSC and Pal as 60 and 50 Hz respectively. In addition, both standards are interlaced. It is important to note that since computer monitors and televisions are both analog devices, the number of colours is not a factor here. To compare this to computer video modes, we have to do a little bit of hand-waving, but basically, the best North American televisions can't display more than about 500 lines. This roughly translates to a maximum of 500 vertical pixels. In addition, the video amplifiers used in televisions are fairly low bandwidth devices, and can't handle high horizontal resolutions like 1024 or 1280 pixels. What this boils down to is that standard televisions can display a video signal derived from up to a 640x480 pixel mode.
To summarize, a VGA to TV converter can be used to translate the VGA's RGB signal to a TV compatible signal for resolutions up to 640x480. This means that the vast majority of VGA/DOS games will display reasonably well on a television since most use 320x200 or 320x240 video modes. Converters that claim to handle higher resolutions have scan converters in them that reduce the effective resolution to that of NTSC or PAL television. i.e. You simply can't display better than 640x480 on a TV.
Some PC to TV converters are listed in the Chipsets section of this FAQ.
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