Comment by throwaway81523
2 years ago
Nice, and the Grandstream adapter is good to know about. There is a gadget now called cell2jack that lets you use your old land phone as a mobile handset but going to VoIP is also interesting.
Quite a while ago, Sparkfin sold a rotary phone that had been modified to have a mobile phone board inside, but it is now long obsolete:
https://www.sparkfun.com/products/retired/287
I still have an old rotary phone around, with the carbon granule mic those things had. It sounds awful. Idk whether that's due to its age, or because those mics just sounded bad compared with modern condenser mics.
I have been thinking of getting a cell2jack to have a pseudo-landline at mom's, since there are people there who get confused by smart phones.
This board also looks promising:
https://www.keyestudio.com/products/keyestudio-raspberry-pi-...
Unfortunately GSM modules in that style no longer work because the 2g and 3g networks are now shut down around here.
Take that carbon mic element and tap it repeatedly on a hard surface to loosen up the granules of carbon that need to be able to move round in there when you speak into it. You may find that it improves the fidelity noticeably.
That's great, I didn't know about those.
For anything that an adult depended on, especially if I didn't live with them, I'd prioritize simplicity and robustness over almost everything else.