Working VoIP Payphone Installation

Payphones, while once ubiquitous, are a rare sight these days. However, a variety of these tank-like communication devices are available for sale, making them prime targets for modification. In the case of the 970-HA-JOKES project, one of these phones was converted into a sort of public art installation, where users could make calls anywhere in the world for a mere nickel.

The build started out with a conversation between the project’s author Nate and his wife about how it’d be funny to put a payphone in a location where a parking meter was formerly… parked. This started him down a very long rabbit hole, purchasing, then heavily modifying a PP100 model payphone that included an enclosure and pedestal for mounting.

Nate's write-up is an interesting journey intro into payphone technology. While nominally a piece of electronics, the real challenge in building such a device is hardening it against aggressive actions, and the environment itself. With decades of development behind it, this phone includes a number of interesting tricks, and weighs in at 45 pounds sans pedestal/shroud.

To hack the unit, Nate added an Arduino-compatible board to detect keypad tones, as well as interface with the coin acceptor. A VoIP device makes the actual calls, which involved an Ethernet to WiFi bridge, plus a bit of antenna hacking to get a signal out of the metal case. The Arduino is also able to switch between this and an MP3 module via a relay, which enables various Easter egg clips to be played with the correct inputs.

The installation was powered remotely with a LiFePO4 battery, and deployed for around 10 days. During this time, there were 406 interactions, and even 47 paid calls. Nate counts as a “huge success,” entertaining many people, and likely confusing even more!