One Ring to Rule Them All: Wiring Radios to Laptops the Hard Way

At Lysk, we process and analyse military voice communications. In other words: we plug radios into computers. This is typically done with an AUX audio cable: a proprietary connector to the rugged radio on one side, and a humble minijack plug on the other.

A Ukrainian Himera military radio plugged into a Macbook, via Himera’s proprietary connector

Getting the cabling right to run our software is surprisingly hard. It’s not as easy as just “plugging in the cables”. And yes, running around in an armoured truck with an oscilloscope is a lot of fun. But what do we even look for when using the oscilloscope? What exactly is carried over a typical audio cable? More importantly: what is 0.7746 Vrms and what do telephone operators have to do with all of this?

Let's start with a quiz about the humble analogue audio cable:

Where does the "jack" connector, the "minijack" predecessor, come from?

Is the audio signal AC or DC?

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