David WE Roberts wrote
Asterisk PBX
functionality
Some people have ACR making payback in a year or so though CTR has one feature (barring a number even though it was withheld) than no home-based box can match.
Out of date costs (1st May 04) Choose to Refuse (CTR) - £3.35 per month. Anonymous Call Reject (ACR) - £4.00 per month.
As others have noted the Truecall unit works out of the box @ £100