A Working Intercom From Antique Telephones

February 9, 2026 by Bryan Cockfield 12 Comments

Although it can be hard to imagine in today’s semiconductor-powered, digital world, there was electrical technology around before the widespread adoption of the transistor in the latter half of the 1900s that could do more than provide lighting. People figured out clever ways to send information around analog systems, whether that was a telegraph or a telephone. These systems are almost completely obsolete these days thanks to digital technology, leaving a large number of rotary phones and other communications systems relegated to the dustbin of history. [Attoparsec] brought a few of these old machines back to life anyway, setting up a local intercom system with technology faithful to this pre-digital era.

These phones date well before the rotary phone that some of us may be familiar with, to a time where landline phones had batteries installed in them to provide current to the analog voice circuit. A transformer isolated the DC out of the line and amplified the voice signal. A generator was included in parallel which, when operated by hand, could ring the other phones on the line. The challenge to this build was keeping everything period-appropriate, with a few compromises made for the batteries which are D-cell batteries with a recreation case. [Attoparsec] even found cloth wiring meant for guitars to keep the insides looking like they’re still 100 years old. Beyond that, a few plastic parts needed to be fabricated to make sure the circuit was working properly, but for a relatively simple machine the repairs were relatively straightforward.

The other key to getting an intercom set up in a house is exterior to the phones themselves. There needs to be some sort of wiring connecting the phones, and [Attoparsec] had a number of existing phone wiring options already available in his house. He only needed to run a few extra wires to get the phones located in his preferred spots. After everything is hooked up, the phones work just as they would have when they were new, although their actual utility is limited by the availability of things like smartphones. But, if you have enough of these antiques, you can always build your own analog phone network from the ground up to support them all.

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A Buzzing, Flashing Phone Ringer For The Elderly

October 11, 2023 by Kristina Panos 8 Comments

For a lonely person, elderly or otherwise, the sound of a ringing phone can be music to the ears, unless of course it’s another spam call. But what good is a phone when you can’t hear it well enough to answer?

[Giovanni Aggiustatutto] was tasked with building an additional ringer for a set of cordless landline phones belonging to an elderly friend. Rather than try to intercept the signal, [Giovanni] chose to simply mic up the phone base that’s connected to the phone port on the router and send a signal over Wi-Fi to a second box which has a loud piezo buzzer and a handful of LEDs.

At the heart of this build is a pair of ESP8266 Wemos D1 minis and an Arduino sound sensor module inside a pair of really nice-looking 3D printed boxen that may or may not have been inspired by an IKEA air quality sensor. On the receiving side, a green LED indicates the system is working, and the red LEDs flash as soon as a call comes in.

All the code, schematics, and STL files are available for this build, and between the Instructable and the build video after the break, you should have no trouble replicating it for the hard-of-hearing in your life.

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Retro Wall Phone Becomes A Doorbell, And So Much More

November 20, 2018 by Dan Maloney 5 Comments

We have to admit that this retasked retro phone wins on style points alone. The fact that it’s filled with so much functionality is icing on the cake.

The way [SuperKris] describes his build sounds like a classic case of feature creep. Version 1 was to be a simple doorbell, but [SuperKris] would soon learn that one does not simply replace an existing bell with a phone and get results. He did some research and found that the ringer inside the bakelite beauty needs much more voltage than the standard doorbell transformer supplies, so he designed a little H-bridge circuit to drive the solenoids. A few rounds of “while I’m at it” later, the phone was stuffed with electronics, including an Arduino and an NFR24 radio module that lets it connect to Domoticz, a home automation system. The phone’s rotary dial can now control up to 10 events and respond to alarms and alerts with different ring patterns. And, oh yes – it’s a doorbell too.

In general, we prefer to see old equipment restored rather than gutted and filled with new electronics. But we can certainly get behind any effort to retask old phones with no real place in modern telecommunications. We’ve seen a few of these before, like this desk telephone that can make cell calls.

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Classic American Dial Phone Gets A GSM Makeover

April 18, 2018 by Dan Maloney 14 Comments

For sturdy utilitarianism, there were few designs better than the Western Electric Model 500 desk phone. The 500 did one thing and did it well, and remained essentially unchanged from the mid-1940s until Touch Tone phones started appearing in the early 70s. That doesn’t mean it can’t have a place in the modern phone system, though, as long as you’re willing to convert it into a cellphone.

Luckily for [bicapitate], the Model 500 has plenty of room inside the case once the network interface is removed, because the new electronics take up a fair bit of space. There’s no build log per se, but the photo album makes it clear what’s going on. An Arduino reads the hook switch and dial pulses, while a Fona GSM module takes care of the cellular side of things. It looks like a small electret mic and a speaker replace the original transmitter and receiver. As a nice touch, the original ringer is used, but instead of trying to drive it electrically, [bicapitate] came up with a simple cam mechanism on a small motor. Driven at the right speed, the cam hooks the clapper arm, rings one bell, then releases it to let the clapper spring back to hit the other bell. Everything is powered by a LiPo, so it could be taken to the local coffee shop for some hipster hijinks.

We’ve seen similar retro-mods like this before using phones from all over the world; here’s a British take and one from Belgium, both using phones with equally classic lines.

[via r/arduino]

Old-school Rotary Phone Gets GSM Upgrade

November 18, 2015 by Dan Maloney 12 Comments

Sometimes, the answer to, “Why would you bother with a project like that?” is just as simple as, “Because it’s cool.” We suspect that was the motivation behind [Dirk-Jan]’s project to make portable versions of classic rotary telephones.

On style points alone, [Dirk-Jan] scores big. The mid-1950s vintage Belgian RTT model 56 phone has wonderful lines in its Bakelite case and handset and a really cool flip-up bail to carry it around, making it a great choice for a portable. The guts of the phone were replaced with a SIM900 GSM module coupled with a PIC microcontroller and an H-bridge to drive the ringer solenoids, along with a Li-ion battery and charger to keep it totally wireless – except for the original handset cord, of course. The video after the break show the phone in action both making and receiving calls; there’s something pleasing on a very basic level about the sound of a dial tone and the gentle ringing of the bell. And it may be slow, but a rotary dial has plenty of tactile appeal too.

Rotary-to-cell conversions are a popular “just because” project, like this conversion designed to allow an angry slam-down of the handset. The orange Siemens phone in that project is nice and all, but we really favor the ’50s look for a portable.

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Antique Phone Doorbell

May 13, 2009 by Caleb Kraft 30 Comments

doorbell

[Bryan] sent in this cool doorbell he made out of an antique phone. After seeing similar phones for $150 to $399, he picked one up on ebay for $10. After some cleaning and polishing, it was looking fantastic, but fairly useless. At this point, he broke it open and started hacking to turn it into a wireless doorbell. He picked up a cheap wireless doorbell and proceeded to gut it. The transmitter side got an aesthetic overhaul, a big fancy button and nice LED in a 50’s style were added. The receiver side got hacked up as well. It was incapable of pushing the required voltage to ring the phone’s bell, so he had to do some searching for a better circuit. Since his knowledge of electronics was limited, he was looking for something that could be plugged in and work without much modification. Eventually, he found the Silvercom AG1170-s5. At $7, he swiped it up quick. It may be a bit of overkill, but he’s using an arduino to trigger the whole thing when it receives the signal. You can download the Arduino sketch on the site.