I have a "land line" telephone (ie. with an RJ11 plug) and a CSR8615 HFP bluetooth module (datasheet) — I'm looking to make my mobile's phone calls ring the land line phone, as well as being able to take the calls there as well.
I'm fairly confident I can get the Bluetooth board set up to collect a line in and send a line out, but I'm struggling to figure out how to make my telephone collect & send audio as well as making it ring.
There's a wealth of resources out there (the 'ringer' section in here looks particularly promising), but so many of these articles are old/incomplete enough that I'm finding it hard to tell whether they're about UK or US telephone systems, and whether I'll end up damaging something if I try putting a 80V peak-to-peak AC voltage through my phone, as is suggested here.
Can anyone offer a design or advice for me? (I'm a professional software engineer, so I can learn fast, but I finished my electronics A-level 10 years ago, so the EE side of things is rusty to say the least!)