Your answering machine will be set to switch on if the phone isn't answered after a certain number of rings. So is the 1571 service, but the number of rings is lower - so it cuts in before your answering machine does.
Somewhat annoyingly, you can't change the number of rings that the 1571 system uses. So you're left with two choices:
a) Get the 1571 service removed from your phone. (You have to ring Sky and allow a few days for the change to take place). That will allow your answering machine to continue taking messages after the same number of rings as you've currently got it set to. The downside is that you won't have the 1571 service available to take calls when you're already on the line (or while your answering machine is still recording a prior call)
OR
b) Reduce the number of rings that your answering machine is set to. (5 seems to be OK. See my link below). That will mean that it cuts in before the 1571 service can. It has the advantage that you'll still have 1571 to take incoming calls when you're on the line. The downside is that you'll have to run faster to get to the phone before your answering machine cuts in!
Answer largely sourced from here
http://helpforum.sky....switches-to/td-p/8055
(together with my similar experiences with BT's 1571 system and my own answering machine!)
Chris