Digital av adapter for iphone 4?

I just got one & i wanted to mirror the picture from my phone on the tv and whenever i use the cord and plug the hdmi cord in it just says no signal but i always plugged in my phone charger to see if the cord works at all and it still charges my phone… What can i do to get the cord to work for my tv? I've tried it on every tv in my house and it just says no signal

Check out the HDMI to HDTV Digital AV Adapter Cable for iPhone 4 4S iPod Touch 4G / New iPad 2 http://amzn.to/....to/TQEheo