Retro Phone

“You youngshit,” my coworker called me, after I mentioned I was “impendingly 23”. Needless to say, my only experience with POTS phones was when I was very young, with my grandfather having a phone and LifeAlert at home. After he went to a nursing home, that disappeared, and I never touched another POTS phone for over a decade.

That changed a few weeks ago when a friend of mine showed me his red rotary phone. Seeing it plugged into his Cisco VoIP adapter was one thing, but I was immediately hooked when I heard it ring. “That’s it, I’m buying one” I thought, as I opened up eBay to find one.

Living near Offutt Air Force Base, I have been many times told about the “Red Phone” that used to be installed there. For those not familiar, that phone was installed in the Cold War era, which was the “holy shit we’re getting nuked, fire back at the Soviets” phone. The Strategic Air Command, which was headquartered at Offutt, was one such place where the phone was installed. I figured it was only fitting given I live in the area to have a red phone too.

(By Clarknova - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=120332499)

Along with the phone I picked up a Grandstream HT802 ATA to adapt the very analog phone to my very modern IP phone system. It was recommended to me as it is known to support pulse dialing. Finally both arrived, and unfortunately the phone was a little worse for the wear:

I want to be clear: this is the exact condition I found the phone in when I opened the package. The seller just put the phone in a box and sent it. I did not remove any packing material. The box only had the phone in it and nothing else. The phone was quite sad, and in worse condition than the pictures from the listing. It wasn’t horribly damaged besides a bent stop on the dial and some scratches on the casing.

After configuring the ATA for my SIP server and enabling pulse dialing, I plugged in the phone, and tried to call my softphone - sure enough it rang after a couple seconds. But the receiver on the phone didn’t work - there was no audio.

The cable was very old, dirty, and too long, so I swapped it. This seemed to fix the receiver issue as well, so I suspect there was a break in the cable somewhere.

After swapping, I broke out my oscilloscope just to verify everything was hunky-dory. I was anticipating having to check the receiver side of the terminal blocks to see if there was a signal coming from there, but I didn’t have to. Immediately after I picked up the phone I heard a dialtone and saw waveforms when I spoke into the transmitter, so it all seemed to work.

The dial was the last part I needed to work on. As delivered, the dial was definitely sad. It wouldn’t fully return from the 1 position, and when returning from a number higher than 4, it sounded horrible and struggled to reset. I disassembled the dial, pulled apart the plastic shield, and took it to the garage to lube it up. Clock oil seems to be the best thing to use here, but I don’t have any nor knew where to get any, so I used some silicone lube after reading suggestions from a forum. I gave each contact point a few drops from the bottle, and a couple drops in the mesh point of each gear, and it immediately woke the mechanism up. It was much smoother and reset a lot faster after adding the lubricant. I was honestly amazed how much that would make a difference, I was expecting to have to adjust the spring tension to get it to reset better. The mechanism of it is surprisingly simple. I’ve never had a chance to really look into old rotary phones but it gave me a huge respect for the engineering of it all.

After buttoning it all up, the dial mech worked far better, the receiver works, and the handset cable was far shorter and less disgusting. I’m super happy with how it works now, and I have my own phone number routed into it as a pager. It was really fun learning how the rotary phone works too, and even that you can flash the hook enough times to dial a phone number (that’s all the rotary dial is doing - it just dis/re-connects the hook as many times as the number is).

Next I think I want to try to cram the ATA inside of the phone, probably around where the “SLIC”/exchange-to-phone interface of sorts is inside (I’ve heard it referred to as a “network” box, but I suspect it’s a bunch of transformers inside). Then I want to add an RJ45 plug on the back connected to a cable (similar to how it currently works - just with cat5e versus cat3). This feels fairly possible, and I think I can shrink down the network interface with more modern components especially since it doesn’t need to haul all the way back to a telephone exchange - just a few inches into the ATA inside. Maybe as more of a stretch, I want to put a cell modem in it to use as a cell phone, with a battery, so you can take your piece of history with you and make calls wherever. But not to mention just making everything fit between batteries and the modem and antenna, also VoLTE is a thing - it makes it a lot harder to do with an embedded solution that isn’t VoLTE aware. The easier plan might be to make the phone a bluetooth headset that pairs to a normal mobile phone (and wouldn’t require a separate cell subscription). Those are definitely more long term though, and I’m incredibly happy with the phone now.