NTL VS1003 Cordless Phone Problem

Question

Hi I've been given a secondhand set of NTL VS1003 Cordless Phones and don't have an instruction manual.On the third handset the antenna symbol has a "?" next to it! I assume this means that the handset isn't paired to the base.If this is correct how do I get it to pair up and do you have any manuals for this model of phone that I can download?Thank-youSimon