This Vintage Phone Is Off the Hook

Before the cell phone took over the world of communications (and started to demand all of our attention) two decades ago, a person’s telephone would be a permanent fixture in their home. The connectivity afforded to us by modern smartphones has unquestionably benefited us greatly in many ways. Now we can contact anyone in the world from wherever we happen to be, and the entire internet is likewise always available at our fingertips.

But, as they say, there are two sides to every coin. Constant availability means that we cannot get away even when we would like to — like when we are on vacation. In the past, a phone could go no further than the wire attached to it, so if someone called while you were away, they would just have to leave a message (if an answering machine was available, that is). And aside from that, it was a whole lot easier to call someone and tell them that they better go catch their refrigerator if they acknowledged that it was running before everyone had caller ID!

Nostalgia for this bygone era has fueled an interest in old telephones — especially rotary phones — among hobbyists. They can be quite beautiful and inspire our curiosity, so many hardware hackers like to convert them into something that can be used in today’s world where landlines are quickly vanishing. Since older phones, like the GPO 746 rotary phone that yaymukund recently hacked on, were designed to be serviceable, this is often easier than you might expect.

For this project, yaymukund wanted to have the phone play music through the receiver whenever the handset was lifted. That may not be especially useful, but it does make for an interesting piece of art — and it also gives one an authentic experience of what it was like to wait on hold in the 1970s!

By sticking some modern electronics inside the case, the goal was relatively easy to achieve. A Teensy 4.0 microcontroller (a 4.1 would be fine as well) was paired with a Teensy Audio Shield to play music, which was stored on an SD card. The hardware is powered by a AA battery pack so that you do not have to rely on an actual landline (or USB cable).

Once the hardware was sorted out, it was just a matter of using a multimeter to find the right fork terminals inside the phone to wire it up to. First, the terminals associated with the hook had to be found so that the device could turn on and off when the handset was lifted. After that, the terminals wired to the speaker in the receiver were located, and these were used for the output from the Audio Shield.

The GPO 746 was more popular in the UK, but if you are on the other side of the pond, yaymukund suggests that a Western Electric 500 might be more your speed. In any case, the conversion process should be quite similar. If you want a music-playing rotary phone of your own, be sure to check out the detailed project write-up. You will find plenty of helpful tips, pictures, and even source code to help you along.