tv out cable

[jc69817]

Hi guys
can anyone tell me the difference between a tv out cable for iphone 3g (?3 ish) and iphone 4 (?13 ish)
i presume there must be some difference

also
i have seen some that plug into the headphone socket and others into the docking socket on the bottom

many thanks in advance

[aftermath]

the cheap 3gs ones are crap and wont be compatible, i paid ?15 for mine on ebay and it has a usb plug on as well to keep charged.

if you look on ebay , it should say if its compatible for different versions of iPhone

this is the one i got
http://cgi.ebay.co.uk/AV-TV-USB-Vide...item53e5734cde