Aren’t you making this a little too complicated? There are senior phones with good decibel increases and large caller ID. Perhaps one will work for her?
http://www.productsforthedeaf.com/category/27715307
Perhaps, and as you suggest Plantronics makes some really nice base station/ handset 50 dB amp’d, large display units. The hand sets are ~$100, and the base station is about $150. Not too bad, and probably worth the money, certainly if they make Mom happy. I may indeed buy them for her. Also, this is perhaps a temporary situation, as my dad is coming home tomorrow after hip replacement rehab. He sees and hears just fine, but won’t be fully mobile again til probably December. So if I could slip in a ‘cheap’ solution for a bit, so much the better. AT&T is our PSTN provider, and they have a really nice selection of devices. Finding that was a pleasant surprise.
The PC solution is IN ADDITION TO conventional ideas.
Since my mom is also not terribly mobile (bad knee) the idea is that she can see and hear across the room, and make a decision to get up or not, without having to keep track of a handset(s).
This is about options and innovations.
It’s all good.