Snodfrey

OK, forgive my total ignorance on this. I want to record calls on my Mac (OSX), I have Vonage internet phone and a cordless phone. It looks like the phone to computer connector I need is this one, because I'm using Vonage. Right? My question is, it says it connects to the handset, so will this work on a cordless phone? I just want to make sure before I spend $50. Thank you in advance.