Any positive talk of using POTS lines was someone else, or me answering Mike.
POTS lines are not really an option because that ties essential kit to a physical location. It would also involve a cease/reprovide to another location should a committee member resign.
I believe that you can do call screening with just a modem - this picks up the call immediately and screens it, then either drops the call or holds it for a handset.
I can't remember how it generates a ring tone to indicate that a call has passed screening.
There is a wealth of information out there - but it is a while since I read up on it and can't find the specific software I was proposing to use. I think it was a variant of Asterisk, but wouldn't swear to it.
discusses one aspect - which suggests that a PCI modem in a PC may be more effective than a USB modem with a Pi for some functions.
Anyway, if you Google for call screening blocking Pi you should find loads of useful information.
If there is broadband Internet access available, there is absolutely no need to get a second physical landline installed, with its attendant installation and line-rental costs.
All that is needed, is an IP phone or ATA plugged into the existing router which will cost about £20, and a free account with Sipgate Basic which includes a phone number of the geographic STD area of your choice.
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