German maker Ulrich Pech has spliced a Raspberry Pi into a vintage rotary phone so it will ring whenever one of his servers goes down.

To do this Pech used several services which check the servers connected to his Amazon Web Services Account. It’s explained in this diagram, but it all hinges on a CloudWatch alert which creates a Simple Notification Service message which the Raspberry Pi Zero W inside of the phone can pick up.

When it does, it sets off the phone. Picking up the handset will relay a machine-read text message explaining what the error is.

The software behind that process is a bit more complex than our explanation, so make sure you check out the full code on GitHub.

Looking back at the hardware and it’s also more complicated than it seems. Due to problems making the phone from 1983 ring properly, it was bypassed entirely and the original ringing mechanism was removed.

Instead the two bells inside are activated by solenoids bought off of Ebay, which are controlled by a circuit connected to the Pi Zero W.

That circuit diagram, links to the aforementioned code as well as more information on how this build was created is available on Hackster.io.