Show HN: Mum's 80th birthday present- a rotary phone from the 1970's
fourlightyears.blogspot.com
fourlightyears.blogspot.com
At home, I still use a W48 [0], I bought somewhere in the mid-90s on a flea market. Just have to change the carbon capsule microphone every twenty years or so. In doubt, one can change to a simple transistor circuit microphone. My router has a phone jack that provides enough voltage to the bell. Works like a charm.
I was worried for a minute... https://en.wikipedia.org/wiki/W48
If its ivory or you like to tinker, you could fix it. Probably just a capacitor or coil. You can find the circuit diagrams online.
If its not or you want to spare yourself the hassle , just buy another one. You may even buy a shiny 'new' W48, albeit not cheap:
https://www.manufactum.com/telephone-w48-a67326/
There also is a german shop selling 'new' spare parts if you need new microphone capsules. Sorry, the website is not in English:
They got FIOS a while back. The tech that showed up was gobsmacked that the phones still worked after the install.
Pic: https://www.oldphoneshop.com/products/4-prong-plug-telephone...
There's a guy in Australia who makes little in-line adapters that translate the pulses into touch tones. It's about the size of a U.S. wall jack, line-powered, and works very well.
I've had it for something like ten years, so I'm afraid I don't have any contact information. But if he's making them, someone else might be doing the same.
Here's a video I made mainly for myself so no polish at all: https://www.youtube.com/watch?v=jjLPGDQlgKQ
Here's the Python code: https://gist.github.com/bootrino/9c6c82e3243782da23308e50a38...
In short I installed a Raspberry Pi Zero into the case of the phone. I considered using an esp32 but the Raspberry Pi is alot more straightforward because I can simply run Linux and code in Python. On the esp32 I could write the code in C++ but it would take longer, or use micropython for esp32 but that no doubt would be harder than the Raspberry Pi.
I found several YouTube videos and also some web ages that described how to connect the rotary dialler to the GPIO pins on the Raspberry Pi, and I found some example code that captured the number dialled on the dialler.
To connect the speaker in the handset it was a little more involved. First I had to work out which wires coming out of the handset cable were the speaker wires - there were four wires coming out, two yellow and two pink. I screwed off the speaker portion of the handset and pulled out the speaker, revealing two yellow wires. The Raspberry Pi zero does not have an audio out port. So I bought the cheapest possible USB audio card for about $20 https://www.centrecom.com.au/shintaro-usb-audio-adaptor-with... and also bought a 3.5MM audio cable which I cut and stripped back the two wires and connected them to the two yellow wires from the handset speaker.
I knew that the hangup/pickup switch must allow/deny a flow of electricity, so I got out my cheap multimeter and started randomly touching parts of the phones circuit board in two places, and lifting and pressing the hangup switch. Eventually I found two points which resulted in electricity flowing or stopping when the switch went up and down, so I knew this must be right connection points, which I then connected to two of the GPIO pins on the Raspberry Pi.
I removed the wire which connected the phone to the plain on telephone line and instead put a USB power cable there.
At this point I had worked out how all the various bits and pieces worked so I wrote a Python program to tie it all together.
When the phone handset was lifted, I played a dial tone audio file. I had about 60 audio files, which I uploaded to the Linux file system. I gave each audio file a number from 100.mp3 to 160.mp3 so when a phone number was dialled, I searched a list of the files, and if the dialled number matched an mp3 filename then I played that file.
I had to remove the bells from the phone unfortunately to fit the computer in.
One of the disappointing things is that it is not possible to make the phone ring because the ringer requires a much higher voltage than can be generated by a small computer. You could probably fake this by installing a small speaker and just playing the sound of a phone ringing.
Credit should be given to the various people who've written blog posts and on YouTube who have done something like this before me - I read lots of pages and viewed lots of videos that do this in differing ways. This guy was most helpful: https://www.youtube.com/watch?v=JChn7tV_qBk. also this person is a real inspiration, she's very creative: https://www.youtube.com/channel/UCEFrHGqsKTvBXk0FC-q_iag. and this guy takes a completely different approach which does not require pulling the phone apart: https://www.youtube.com/watch?v=siwq1FxvRrw
> One of the disappointing things is that it is not possible to make the phone ring because the ringer requires a much higher voltage than can be generated by a small computer.
Voltage can be stepped up using a transformer, no problem. It's that you need 20~25Hz AC and a certain amount of current (see "ringer equivalent" calculations). Either way, you're probably right to skip it for this project :)
I mean that’s not quite true. A magicjack which is basically an ATA is about the size of the Pi Zero and produces ring power. A REN is on the order of 10 mA which at 90V can be generated by a very small (like smaller than a dime) switcher.
Indeed the quickest and easiest way to “modernize” an old phone is probably to stuff the guts of a readily available analog telephone adapter and interface it to a Pi, or a Wi-Fi adapter, etc.
You might even dispense with the pi: https://randywestergren.com/reverse-engineering-obi200-googl...
http://www.classicrotaryphones.com/forum/index.php?topic=203...
Normal phone lines will supply upwards of 100ma, but since you only need to ring one ringer, you can do with less, you can also tune the ringer to make it more sensitive.
That looks like a generic Chinese USB audio card and they are sold for much less where I live (~$1.5). Aliexpress has a ton of them around that price level.
She recently suffered a stroke that's left her confused and unable to engage, and the abruptness of what was a much slower transition into dementia has been upsetting to the family. I'm hoping being able to pick up her receiver, dial her number, and listen to one of the many loving messages she's left us throughout the years will help. She's also deaf now, otherwise it would have been designed like yours.
Eventually I'll deploy it as a PBX so others can call in, but I haven't had much time to test.
My next thought was self-pity. My area had just been assigned a new code: 909. The absolute worst code possible². 28 pulses required for us bumpkins while only 6 were needed for the cool people in the city. :)
[1] There's a good Underunderstood episode on this. Apparently it's not exactly certain this was the rationale. No memo exists detailing it, but it matches up pretty well with how they were initially assigned. (https://underunderstood.com/podcast/episode/area-code-conspi...)
[2] Well, I guess 900 is actually worse, but that's not a geographical area code.
(checking wikipedia [1] ...)
TIL It was also to permit physically blocking all the other numbers in public access rotary phones while leaving emergency calls enabled. Smart.
[1] https://en.wikipedia.org/wiki/112_(emergency_telephone_numbe...
Edit: also, you could call for free on rotary pay phones by tapping out the number on the "hangup" switch.
I never had the coin sound maker, but I did have a small transcription digital recorder years later that could trick the proctor test set into thinking a nickel had been inserted.
I don't remember all the other tests, hopefully there's a webpage somewhere about it.
Back when there were lots and lots of small local telephone companies within a single area code, where I lived you didn't have to even dial all seven numbers.
As long as you were calling within the same phone company, you only needed the last five digits. So calling the neighbor across the street was just 2-3342. But calling someone you knew who was a mile away in a different phone company, you had to do the whole 867-5309. There were some people you knew who lived across the border in another state, and for most of them you had to dial all 11 digits.
But some of the small phone companies operated on both sides of the state line, so you could still dial people with 9-9845, even though they were in a different area code in a different state.
It was also billed as a local call, which made the BBS I ran the main e-mail exchange point between those two area codes for the store-and-forward BBS network I belonged to.
This is true, but there was also a bit of politics.
New Jersey got the lowest/first in order area code (201) because that's where Bell headquarters was.
And since Washington, DC was the capitol, it got the next number in line: 202.
Only very rarely are area codes tinkered with in this manner. The only other one I can think of is 321 for the area around Cape Canaveral.
Was New Jersey the most populous state to only receive one code?
> Only very rarely are area codes tinkered with in this manner. The only other one I can think of is 321 for the area around Cape Canaveral.
That's awesome. It would have been a crime to pass that opportunity up.
Just as an aside, the reason the UK uses 999 as the emergency number is because it was much quicker to dial on a rotary phone.
https://upload.wikimedia.org/wikipedia/commons/thumb/b/b6/Ne...
It's from New Zealand, but they drive on the same side of the road as the UK ))
9 is almost the furthest away from the stop - 0 is further.
999 was chosen because it was less likely that interference would generate the exact same sequence of pulses. https://web.archive.org/web/20090302014433/http://www.btplc....
https://blog.davidv.dev/revamping-an-old-tv-as-a-gift.html
The gist of it was putting a Pi inside a b/w CRT, soldering the GPIO to the tuner and that way you could change the channels. I even put fake static on some of them.
The software ended up horrible as I ran out of time.. but it worked great!
Someone on dslreports.com years ago reverse engenered and worked out the format of the config. file and created a config file creator program as well as a serial script to hook to its TTL serial port to change the address of the TFTP server. I now have it providing two analog lines from voip.ms that have a strong enough REN to power several old analog phones with real bells in the house.
It even allows you to pulse dial class five codes like disable call waiting and call voice mail. EX. 1,1,6,9 = *69 if touch tone dialing.
The controller's of the botnet then spam the encoded instructions on comment sections all over the web.
Phone sex numbers are treated specially in Greece?
> Phone sex numbers are treated specially in Greece?
But I do want to know to know the technical details…. :)
Some other ideas in case people are also looking for other ideas:
- A "safe" dial (when she bought her house they found an old antique safe under the stairs which became a source of some mystery until it was cracked open (it was empty))
- A numeric keypad (my mum used to use this a lot when she worked as a translator and had to memorise the unicode for all the French characters)
- Just a simple box with a big rotary dial knob on the front - can't really think of a good story for this though.
You could buy a portable digital voice recorder and pass it around the family to record their messages. This may not be as much "fun" because most probably won't have the random playback factor.
To get that, you could record the messages and load them up on an MP3 player. That will enable shuffle mode. If doing some sort of custom hardware project was an important part of the idea you could wire up a permanent speaker and maybe do a 3D printed enclosure. You could take it a step further and eliminate the MP3 player and do it on a Pi with some hardware buttons.
If your mum is or was into vinyl records, there are places that will custom press vinyl.
I once had a teenager say it was "complicated" to use; dial 9 for and outside line and the number.
1935 is late for a phone with a subset.
> Is there really a law that makes it illegal to display an antique phone
> that isn’t connected to a phone line?
> Is a box of old cell phones now to be considered a weapon of mass destruction?
> There is no expectation that a device that is disconnected or inoperable will continue to function
If the guts of a phone are replaced then I’d argue that’s no more or less operable then an old cell phone.
I think laws in the context of ensuring that device manufacturers provide reliable 911 service is sensible (ie maybe it should be enforced against Google) - but as some nanny legislation because someone might confuse a display piece is a bit silly in my book. (And think of the elderly as insinuated by the GP is weak and insulting - having dealt with demented parents - whether the phone was connected was of no issue - simply identifying a phone was a bigger problem… meanwhile old people aren’t automatically idiots).
It’s also absurd to think that someone lacking the situational awareness to identify a non-working phone also has the faculties to read some warning sticker. This is something that comes from a corporate legal department not something that normal people would think to do.
One quick fix would be to be that if someone dials 911 the phone immediately responds with 'this device is incapable of reaching 911, please use another phone'.
Two options for getting around that.....
You could install a speaker into the phone and play a recording of a phone ringing.
You could install a little electric motor with a lopsided head on the axel and position it in between the ringer arms and spin it at the correct hertz and it would ring the bells.
I used to take stuff like this apart as a kid. A call came in while I was in the middle of it (yes, I was playing with the incoming wires). Ouch!
> Removing insulation from a live phone wire with my teeth (I had decided to put an extension in my room without asking for help...) was one of mine, that definitely made me more careful. Went just fine until I closed the circuit with my tongue by accident just as someone called. Not pleasant.
HDSL powered the remote card from the one in the central office, using (IIRC) 130VDC.
One time I was at a customer prem troubleshooting an installation. The customer's phone vendor was out there with me as we were hunting for the right cable pairs in the terminal. I was getting ready to call another tech back at the CO to put a tone generator on the line when the phone system vendor told me to just run my fingers across the terminals until I got a shock.
I thought he was joking. He wasn't. He looked at me like I was a weenie and went ahead and did it himself. Dragged his fingers down the line until I saw him twitch. "Binding posts 47 and 48, right there"
I had accidentally shocked myself probably dozens of times, but never as a troubleshooting technique!
By yeah, if it's just a watt, that's going to be on the order of tens of milliamps at 80 volts. It probably wouldn't even need a heatsink.
You can, provided you also add a boost converter [1] to generate the ring voltage from the input supply voltage.
Any basic ATA will easily drive a ringer.. ever seen a MagicJack? - it’s a complete USB telephone adapter and barely larger than a thumb drive. They aren’t greatly hackable - but something like a Grandstream HT801 can be opened and the board put inside and you basically have an entire telephone interface right there. They even support pulse dialing.
The phone acts as a familiar medium for new content. You don’t call people with this phone, instead it’s used to hear pre-recorded messages from her friends.
Nor does she have any fond memories of old crappy phones. In the olden times phone calls were so expensive that everytime the phone ringed it was something serious and mostly bad.
The OP was making a present for their grandmother's 80th birthday, in 2021, so their grandmother was born in 1940 or later. Someone in their 80s these days is unlikely to be so cognitively impaired as to be worried by phone calls.
They're more likely to be facetiming with grandchildren from their iPads/iPhones.
In Australia, POTS service was universal and the call costs for local calls was untimed and minimal (perhaps $0.10/call). Timed calls were for longer distances in Australia (STD) or for international (IDD).
Unless you're talking about up until the very early 80s, when long distance / international calls required operators.
So even if you still have copper, it doesn't have POTS service available on it. You'll be connecting to a FTTN/B/C (node/building/curb) service.
They are in this age range and now prefer to call people on their iPad.