Making VoIP Calls with Antique Rotary Phones | Hacker News Reader

Making VoIP Calls with Antique Rotary Phones

nbailey.ca

45 pointsyabones30 comments

This takes me back! In the 1980s, I lived in a small town, and my Dad learned that the phone company still offered "party line" service for cheap - you could share a piece of copper with everyone on your street. I guess for most of the 20th century there were social norms about how to ask to use a shared phone line, how to know if a call was for your house instead of for a neighbor's house, etc - but by 1980 or so, everybody had household-private lines. So my Dad's insight was that he could save some bucks by paying for party-line service and we'd be the only house using it, so it would be de-facto private. But the side effect was that, since it meant we were using antique hardware at the phone company, it didn't support touchtone dialing! So we kept some 1960s-era rotary phones around, and when we got new phones we had to find the little hidden "tone/pulse" backwards-compatibility switch on the handsets (and my geeky friends would come over, click the touchtones back on, try to use the phone and say "hey, your phone is broken!" dude, you broke it. Presaging a long career in tech support, I suppose)

We had to switch to modern lines after we got a 1200 bps modem. Someone from the phone company called and said "you've connected an electronic device to the party line, that's not allowed, 'cause how would your neighbors let you know they need to use the line?" apparently the argument "we're the only house on this line!" was not convincing. So touchtones started working, and presumably Southern Bell got to retire the last party line hardware at the switching station.

So I've long wanted to do some kind of hacking with a rotary phone! I've seen lots of DIY projects that use analog phones as audio inputs, but they almost never including dialing, so this is exciting to see! I've always assumed you'd have to build your own pulse-counting circuit, I had no idea there was a commercial option, that's kind of mind-blowing, but I suppose they were needed to support old hardware.

It's interesting to me how frequently on HN I read about people using their formidable technical expertise to pursue projects with really impractical and anachronistic technology, whether it's this project, or retrofitting some really old laptop with scarcely any processing power, or whatever. I understand the impulse to reject practicality and not let "the market" or merely pragmatic considerations dictate one's creative/intellectual impulses. But there is also something perverse about devoting so much brainpower and energy to these kinds of niche projects, which seem almost like a sort of performance art or a thought experiment made real. I find it kind of appealing, but also kind of odd.

I've thought about this often. My conclusion is that ~all humans "waste" time in some manner or other -- and that this is natural, probably necessary, and good.

The same argument can be made for sleep. And there might be a useful analogy there...

Psychologically "sleeping" (i.e. directing your energies in not-obviously-productive pursuits) bends your brain in a way that a relentless focus on "useful" work does not. This is probably true of all entertainment.

Objectively, the person who spends 500 hours getting a 6502 emulator working in JavaScript and then blogging about it, has added more to the world than the person who spends those same hours streaming The Simpsons.

...and also more than those of us who spend 500 hours reading the blogs of people who made crazy useless things happen...

But maybe the personal value of the diversionary time spent has some sort of parity..?

It occurs to me to that sometimes "silly" projects can also lead to practical applications. Mainly I think I'm struck by how many techy people have the impulse to pursue these quirky projects, and how there is sort of a poetic spirit to it under the techy exterior. As you say, it's certainly a more interesting and creative use of time than sitting on the couch watching TV.

Every time I work on something anachronistic or artificially constrained, I learn more about the fundamentals of the cutting edge stuff.

There's a way that the "default" perspective of the industry tends to emphasize certain skills and knowledge and de-emphasize others, but the world of useful skills is much broader than that, and things crop back up in unexpected ways. Maybe we'll never need to make calls with an antique phone, but there could totally be audio and telephonic applications on modern hardware where the average engineer would have no idea what to do, but someone who had worked on a "toy" project like this would be able to say "oh, this is just like an old [whatever]"

For anybody else wanting to do this, you'd be better off picking up a Grandstream 80X ATA. It supports pulse dialing, pulse to tone conversion, 'high power' ringing, and decently modern TLS. If you're good with a soldering iron and have a 3.3v TTL serial cable, you can also pick up really cheap used Vonage HT802s and 'unlock' them.

I have a commercial box which connects an analog phone to a Bluetooth connection. It even generates ring voltage. (88 volts, 20hz). In this video of our old steampunk telegraph office, the phone in the foreground is fully functional. It's tied to a cell phone and can be used to make and receive calls. It's not really an antique phone, though; it's a 1970s reproduction. Strangely, it came with the connector for Japanese phones, and I had to find the mating connector for that.

We let kids try it. One 7 year old said, picking up the handset, "It's so heavy".

At home, I have several analog phones tied to a VoIP box on Sonic. They use the old house phone wiring, which is no longer attached to the telco. Plugging the VoIP box into a phone outlet drives them.

[1] https://vimeo.com/97062822

What's the Bluetooth box, if you don't mind me asking? I have a reconditioned Southern Bell payphone I purchased years ago to benefit their retiree organization. The device you're describing would lower the barrier to entry enough that I might actually do something (since I could use my existing cell service vs. provisioning VoIP service).

There are several interface boxes, such as Cell2Jack. Mine is packed up right now, so I don't have the brand info.

Coin telephones have a slightly different interface. But if it's been "reconditioned", the coin control system was probably disabled and it just acts like a ordinary analog phone.

Thanks. I'll take a look around for one. Sadly they did remove or disable the coin handling circuitry so it's just a funny analog phone now. I really should try to crack it open and see what's inside.

For those who don't know how to use a rotary dial phone, here is a 1940 educational movie by Bell Telephone they made to teach customers about this new technology [1].

[1] https://www.youtube.com/watch?v=p45T7U5oi9Q

If you're really interested in this kind of thing check out C*NET: ckts.info. Members have all sorts of old telephone equipment up and available.

Back when I still had a landline I used to "impress" people with my ability to call their cell phone using only the hook switch on my desk phone.

I'm pretty sure I was made aware of this trick from the 1995 Hackers movie, so there is at least one accurate thing in that movie.

> 1995 Hackers movie, so there is at least one accurate thing in that movie.

Recording the sounds that were emitted by a payphone when inserting coins and then playing them back into a payphone handset to get free calls ("red boxing") was a thing that def--err, maybe worked hypothetically I do not know and definitely never tried this absolutely not no way...

Understanding the difference between in-band and out-of-band signaling is valuable. Pay phones and how a red box exploits in-band signaling has been an example I've used in teaching. I find it less difficult to relate than the MF signaling that blue boxes exploited.

Yeah, last I remember it was UPS that they transferred my call and then I heard a couple tones and thought “ohhh, in-band signaling”.

Its a little trickier in New Zealand, where one pulse means '9' :)

https://commons.wikimedia.org/wiki/File:New_Zealand_Rotary_T...

I did something similar to this, and ordered a converter from Australia called DialGizmo, that could handle the two types common here, and probably could be configured for a New Zealand phone as well. Was harder to find reasonable PoE powered SIP adapters. :)

I don't recall if it was in the book, but the 1986 "Manhunter" film (an adaptation Thomas Harris' "Red Dragon") featured Hannibal Lecter abusing a phone with no dialing mechanism by way of shorting the switchhook to dial an operator by flashing. It was a neat thing to know how to do.

I was hoping to see some soldering action, well... Anyhow how would i go to create a home and self hosted VoIP network with 2 phones? Any leads?

I've been trying to figure that out myself. Another post here recommended Grandstream products for connecting analog phones to VoIP. Looking at the user guide for the HT802 you can make direct calls between the extensions. http://www.grandstream.com/products/gateways-and-atas/analog...

Unfortunately there system requires dialing "*701" or "*702" and dialing star on a true rotary phone isn't possible without some other system in place. Like this product from dialgizmo: https://www.dialgizmo.com/how_it_works.html Dialing two consecutive stars would still be annoying and slow.

I've been wanting to wire up an in-house "intercom" system using old phones. I'm a little surprised there isn't a "telephone HAT" for the raspberry pi that will interface directly with an old phone. A HAT that could interpret the DTMF or pulse dialing and drive even the old fashioned mechanical ringers.

I was thinking that there should not be any huge technical problem with making an FXS interface for the raspberry pi, and I did find a USB adapter which I might have been tempted to to try, but it's a little expensive and only supported 0.7 REN (ringer equivalency number) which might not be enough to power the mechanical ringer on an old phone. Further searching did turn up the OAKR2 HAT though ( https://switchpi.com/oakr2-module-specifications/ ) and it looks like the schematics are on github.

The idea is to pick up an old rotary phone and hook it up a raspberry pi which will make phone call over VoIP. The rotary dial will just be the user interface, the mic and speakers will be hooked to the RPI. There are some project on github explaining the project: https://github.com/hnesland/aselektriskbureau I plan to enhance it a bit to use the original ringer with the help of some power electronics.

However I have no clue on how to create a Voip server at home to serve phones locally and assign phone numbers.

have thought about doing not-quite this with a western electric touch-tone capable beige deskphone - anyone have any feedback on good/simple VoIP providers/software for personal use (like 1-2 phone numbers + self hosted PBX/voicemail, remote access over VPN from softphone app a plus)?

I ported a landline to Anveo[1] long ago, and used it to route calls to a gVoice number, which worked pretty well.

1: http://www.anveo.com/

I switched my landline from Verizon to Anveo about 5 years back. They are pretty solid! I barely used my landline so I have the cheapest plan possible.

The provider I use is https://voip.ms

The UI takes some getting used to but the service is cheap and works great. Similar to how I did it, you'd need an ATA box to provide analog service to the phone, and it would talk to your provider over SIP/RTP.

Another option would be a self-hosted PBX box. Asterisk [1] is the tried and true open-source option, but it does have some sharp edges. 3CX [2] is another option, but it's proprietary and has some limitations.

Either way, you would need a provider to give you the 'SIP Trunk' (phone number etc). I think Twilio [3] is the best option for this, but I've been using a hosted service for a while so I don't have much recent experience with this and can't vouch for costs/functionality.

---

[1] https://www.asterisk.org/

[2] https://www.3cx.com/free-pbx-edition/

[3] https://www.twilio.com/sip-trunking

Provider to recommend to your parents or grandparents: Callcentric

Provider for hobbyists who need flexibility: voip.ms

Provider for cheapest termination rates and flexibility: Anveo Direct (not the consumer product)

Bria and Groundwire have good SIP softphones for mobile, but aren't free. Since multitasking on iOS is so limited, these apps can register on their own servers, then send push notifications on calls.

3CX or Asterisk are good choices for connecting to trunks. 3CX is much less flexible, can cost money, but is "easy".

Freeswitch and Signalwire are also good combos. Signalwire is very low cost.

Aren't call calls carried digitally now - ie VoIP.

(fun project).

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