Convertor for Gamecube

This may be a stupid question, but do all convertors work in the same way, or do you need specific ones for specific consoles?

Im talking about an NTSC to PAL convertor, is there one for every console, or are they universal?

Im asking because each one i find on ebay is listed with a console next to its name (im not sure if this is just to be in more search results), such as this:

http://cgi.ebay.com/PAL-to-NTSC-TV [...] dZViewItem

Would that work with a gamecube just as it would with a wii?

Thanks.

Most televisions these days can display both PAL and NTSC signals so you may not even need one. Just something to look into.