Were you looking for the answer machine facility for your mother, or is it more for your use? I'm just asking because we got my mother what we thought was the simplest, big button, telephone answer machine we could find - and unfortunately she was not able to use the answer machine part. Also, because there was an answer machine, I think that people calling her thought that their message got through, when the odds were against, particularly after my mother had tried. The answer machine is now disabled, and it has become a fairly expensive basic 'phone.
We use 1571 and its brilliant. Theres no flashing lights or anything to alert anyone who might try and fiddle () - just the change in dialing tone that I can check up on.
And, yes - as nitram says - its free.