I have a similar project, 90% finished, with a wifi enabled Rpi4 that uses asterix as a soft phone and can be used as a classic rotary. Some notes:
- As the creator of this music phone I had hoped to keep the original mic and speaker. This turned out to be more work than I was willing to do as those were both 24V devices, not suitable for Rpi integration without extra electronics.
- I also had hoped to keep the original handle chord. This also turned out to to be impossible as the original mic and speakers shared a common 24V+. So 3 wires in total in the chord, I needed 4 for the new mic and speaker.
- I also ripped out most of the ringer mechanics, but kept the bells. The bells are now hit with a piece of heat shrink tube on the end of a small motor.
I did the same thing to a numpad phone (also old) about 2 months ago. I squeezed a pi zero-w into the chassis and wrote some software to bind each key from 0-9 to a song and then used the Pi's Bluetooth module to play the sound on a speaker across the room. I also have a button that reads out the current time and it runs a website to upload new songs and change the bindings. It was a really fun project and I am surprised someone had the same idea!
My child is old enough now to stay home alone during short errands. Since we don't have an old school land line it would be cool to take inspiration from a project like this and build her a "red line" device that gives her immediate access to reach me without breaking down and buying her a cell phone yet.
But what would I hack together for the software side of that?
I'd skip the projects and just buy one of the numerous phones that target this market. They make watches, dumb phones, and smart phones, that are locked down and only allow phoning/texting specific people.
The other option would be to get a real copper phone line.
My reasoning is that a real emergency may include a power outage. Relying on some cool hack isn't going to be helpful when your child is trying to reach out to you when there is no power at home.
Unfortunately in my country even landline phone lines don't work on power outages, since with the transition to digital only lines (with VDSL) is the router that inside has an ATA to which you connect your landline phone. In fact you have VOIP phone service at your house (in fact you can avoid completely to connect your phone to the router phone socket and use whatever VOIP phone you want, with the correct settings extracted from the provider router).
Even if you provide backup power to the router is not enough, since at the other end, VDSL cabinets in the street, there is no backup power, so if it's not a blackout of only your house but it insist the local transformer, the VDSL cabinet is probably out of power too and thus no line.
The only reliable solution is 4G that is not so reliable since in case of emergency lines get overloaded.
I probably should get an ham radio license to be safe...
I bought a Cisco SPA112 ATA (VoIP analog telephone adapter) off eBay for under $20 to use with my retro computers, and for my kids I picked up two analog phones at a junk store and set it up to allow dial through to the other one, so my kids could call each other (sitting right next to each other) for free.
The same device can also be configured to use a VoIP provider and with all the configurability of it I bet you can get it to auto-dial when you take the phone off the hook. edit: it looks like yes it is doable https://community.cisco.com/t5/atas-gateways-and-accessories...
The simplest solution for me was to get a "feature phone" that doesn't have apps or anything else enticing, and leaving it in the drawer as an 'emergency phone'. The SIM is on the family plan so it's not a significant expense, and it keeps a charge for about a month as it's off most of the time anyway.
It ends up not becoming the emergency phone and more 'remind xyz to grab abc on the way home' phone but oh well :)
You can buy an ATA (Analog Telephone Adapter) to convert old analog phones to VOIP, and then use it with whatever VOIP service you want. Just be sure that the adapter supports pulse dialing since you want to use it with a rotary phone (not all does).
If it’s being used as a “red phone” (pick it up and it immediately calls the other end), the feature that the parent wants to make sure it has is is “automatic ringdown”.
The software could be pretty simple. Hook a button up to GPIO, write a bash wrapper around one of the command line VoIP clients, write a little program to call the script when the button gets pressed, autorun that one on boot.
I made something similar using another instructable(1) with a simpler approach a couple of years ago. Great fun, and relatively easy to do (it was my first 'hardware' project and I knew nothing about electronics).
I kept the speakers and all intact and it still sounds fine. I loaded it up with some fairytale stories, 1 for each single number you can dial.
I've been meaning to build a similar project for my SO. I want is to be able to connect the rotary phone via bluetooth for calls (only calls) and dialing if possible. Has anyone worked with anything similar that can provide some pointers?
I'm guessing the dialer part should be "simple" as I could probably connect an Arduino as if it were a keyboard but can't find much on the audio part.
I never realized what a perfect rpi case a rotary phone is. You can even fit a usb hub on there. And it can be quite stylish. And durable. And ez to cut the plastic for mods. And cheap. My eyes have been opened. I'd probably strip everything off it tho.
