Raspberry Pi in Rotary Phone




Introduction: Raspberry Pi in Rotary Phone

I found an old Western Electric rotary phone in my attic. It's really an amazing piece of hardware. It seems to work fine several decades after its construction despite whatever abuse it took before ending up in my attic. However, I don't currently need a rotary phone.

So I decided to put a Raspberry Pi inside it. I decided to make it an MP3 player that's simple and robust for my daughter, but I guess it can actually be a general-purpose (if inconvenient) computer.

The pictures show the finished product. My goal was to leave the phone as intact as possible (ars est celare artem), so the main sign anything has changed is that the port on the back is now micro USB rather than a modular phone jack. I also added a switch to power down the Pi in the handle below the hook, but I wish I hadn't -- the handle was really comfortable for carrying the phone and the switch gets in the way. So these instructions don't show that part. Since I wanted to add as little as possible, I put the speakers in the headset.

Step 1: Gather Hardware

Step 2: Prepare Phone

First you have to open the phone and remove the stuff that takes up all the space

Next, I cut a polycarbonate sheet to mount the Pi away from the metal base. I cut with a box cutter, scoring halfway through then cracking at the cut. Then I drilled holes by hand -- I broke some pieces using an electric drill, but maybe I lack technique.

The first picture is the template I cut from. The second picture is the actual sheet I used. Obviously I made some mistakes getting the sheet to look like the template. In particular, I accidentally broke the tab in the upper right, which I still think would be better to have but oh well. Also I put several holes in the wrong places. The measurements on the template are close but I actually drilled by putting the sheet in place and marking.

The third picture shows the sheet with screws attached. These will eventually attach the Pi to the sheet.

The fourth picture shows the sheet mounted to the base of the phone, and the fifth shows the Pi positioned on the sheet.

Step 3: Wiring Phone Devices

To figure out how to use the phone devices as input to the Pi, I used this schematic.

Basically, the hook, the rotary, and the dial can be viewed as independent switches. The hook switch is open when the receiver is on the hook then closes when the receiver is lifted. The dial switch is open when the rotary is in its default position and closes when the rotary is moved away from the default (opening again when it gets back). The rotary switch rests in the closed position, then opens and closes as many times as the number that was dialed.

I wired each of these switches to a GPIO pin using a jumper cable. For each switch, I included a 10k ohm resistor as shown in the wiring diagram. In the diagram, the top color labels describe the colors of the wires in the phone. The bottom color labels are just colors I used but do match what's pictured in the second picture.

To make it easy to connect and disconnect the wiring, I made my own "rainbow cable" by gluing together the jumper terminators. I chose a row of GPIO pins that were all in a line. Specifically I connected to pins 9,11,13,15 and 17 which include a ground (pin 9) and a 3.3V (pin 17) and between them three GPIO pins. I wired the rotary to pin 11, the dial to pin 13 and the hook to pin 15, as shown in the diagram.

Step 4: Receiver and Power

I removed the speaker and microphone from the receiver and replaced both with new speakers. I wired them for stereo through the twirly cord. So that's seven soldering points, shown here.

In hindsight it might have been more fun to keep the microphone and just have mono audio.

After replacing the heavy speaker and microphones with newer lighter speakers, the receiver was no longer heavy enough to keep the hook down on its cradle. The spring would push it back up. So I added some ballast to the receiver, in the tube connecting the mouth and ear pieces.

The power cable was the hardest soldering of the project. The female plug has small tabs, but fortunately we only need two of them to carry power. I caulked it to the rear of the case. The male plug is even smaller but finally I got it to work. To figure out which tabs to used I followed some guides for the male and the female.

Step 5: Put Arch on Your SDcard

You can download the Arch OS for the Pi from archlinuxarm.org

I do all of these steps on a linux box I use. If you want to use something else, look here

Here are the commands on linux:

wget http://archlinuxarm.org/os/ArchLinuxARM-rpi-latest.zip
wget http://archlinuxarm.org/os/ArchLinuxARM-rpi-latest.zip.md5
cat ArchLinuxARM-rpi-latest.zip.md5
md5sum ArchLinuxARM-rpi-latest.zip

The 32 character blobs spit out by the last two commands should match. If they don't something weird may be happening.

To write the image to the sdcard, I use

unzip ArchLinuxARM-rpi-latest.zip
dd bs=1M if=./ArchLinuxARM*.img of=/dev/sdX # replace X with location of SD card

This takes some time.

The image we wrote to the SD card was only 2G. To make use of additional space on the card (if any) we need to resize the partition.

Instructions here

I used gparted on my linux box, and it worked fine.

Step 6: Boot and Install Software

At this point you can put the sdcard in the Pi, connect a network cable, and boot. You should see some blinking lights on the Pi.

Since there is no monitor/keyboard attached to the Pi, I connected remotely via ssh

ssh root@alarmpi.local

The default password is "root" and should probably be changed. I do change it, but since the Pi has no external connections I'm not sure how important that is.

To update the operating system software and install required software:

pacman -Syu nodejs rsync parallel mpc mpd espeak alsa-utils git

This will prompt you to continue by pressing 'Y' or enter. Then it will download and install several packages, which will take some time.

Now there is some software supporting the phone devices, which can be installed with

npm install -g git://github.com/steven-gardiner/piphone.git

When that command completes, to configure the software you can now use

bash /usr/lib/node_modules/piphone/config_mpd.sh
bash /usr/lib/node_modules/piphone/install_crontab.sh

(Optional) If you do use a USB audio adapter then you'll need to configure alsa to use the adapter, using the command


Don't close the ssh session yet because we will use it in the next step.

Step 7: Add Music

The point of this project was to make an anachronistic MP3 player, so we'll want to load some MP3 on the Pi. This step assumes you still have an ssh session to the Pi which we established in a previous step.

(Optional) If you don't have a set of MP3s in mind, these commands will download some Creative Commons samples to get you started

mkdir -p /var/lib/mpd/music/samples
(cd /var/lib/mpd/music/samples; bash ~/node_modules/piphone/samples.sh)

Provided you have some MP3s available on your linux box, you can put them on the Pi with the following commands

On the Pi:

mkdir -p /var/lib/mpd/music

On the linux box:

rsync -av /path/to/music/* root@alarmpi.local:/var/lib/mpd/music/

When this command has completed (and anytime you alter the contents of the /var/lib/mpd/music/ directory) you should run the following command


When that command completes you can tell the Pi to shut down:


You should see the blinking lights dwindle down to a single light which indicates the power is attached. You should now disconnect the power and the network cable.

Step 8: Close Case

At the end of the last step, you powered off and disconnected the Pi from power and network.

Next you can hook up the GPIO pins, plug the headphone jack from the headset into the audio jack, and connect the power cable from the case to the Pi.

Then you can close the case, making sure to massage any wires out of the way of the hook mechanism. Make sure for instance that the plastic tabs that protrude from the hook cradle pop up when the case is closed.

When the case is closed, you're done. You should be able to plug a micro usb cable into the back of the phone and after a few moments the phone will be ready to do your bidding.

With the default software, to power down, you dial "1178." Because of some bugs in the software, you may need to dial it a few times for it to take.

The other commands (you can edit the software to change them) are

1: play the current song softly

2: play the current song loud

3: play the next song softly

4: play the next song loud

5: play the previous song softly

6: play the previous song loud

7,8,9,0: search for a song by title and play it

After playing a song the phone will stop and wait for further input.

Vintage Contest

Runner Up in the
Vintage Contest

1 Person Made This Project!


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Question 2 years ago

Thanks for this! Is there any additional info on the software? I'm getting errors regarding the tts component and wondering if you have a barebones version of your script to debug with first or if there is a minimum nodejs version required/something else missing on my PI?


2 years ago

I used this instructable to convert an old phone booth into a recording and playback booth in my school library. Students use iPads to record book talks. Then, we use VNC Viewer to remotely connect to the Raspberry Pi and upload the recording to the device naming it with one of the numbers on the phone so that it automatically replaces existing recordings. Finally, students listen to the book talks by dialing one of the numbers on the phone. I have included a phone directory inside the booth so they know the book title and who recorded the book talk to help them make a choice. This is a great project to get students of all ages motivated to write and record a creative book talk that engages the listener. It incorporates ELA standards for writing, speaking, and listening. It also gives students an authentic audience for their work and gets them involved in building a reading culture throughout the school. I have included my lesson plan and rubric for evaluating the book talks. It really is more of a checklist and students are self correcting as they listen to model peer examples and strive to make their book talk get the most listens and generate the greatest buzz around the book they selected. It's still a work in progress. I plan to add coding so that I can use one of the numbers as a recording channel. I'd also like to create some code to count and provide an output for the most played book talk. They love this project! Even though they didn't build the phone, I showed them pictures I took of my process converting the old phone into a playback station. It has inspired them to be more creative with our new Micro:bits now that they see the power of microcontrollers to add functionality to other objects.


Question 3 years ago on Step 3

How did you determine you needed 10k ohm resistors?


5 years ago

I would like to use the Pi to turn the old phone into a currently compatible functioning domestic phone, i.e. to serve tone dialing... any ideas, links?


Reply 3 years ago

i'm doing a similar project. I believe the best way to do it is to connect the phone to an arduino (leonardo?) to interpret the signals and have that transmit to a Pi running a VOIP app.


6 years ago

Cool. I will build this one. I am planning for converting an old phone to an IP telephone device only. Thanks.


7 years ago on Introduction

Great job!

ps: you should enter this into the vintage contest if you have not already!