This is how you modify a Maxon VOX unit for use with a computer for APRS.

BOM (Bill of Materials):
Maxon VOX Unit $2
AA Battery Holder $1
3.5 mm to 2.5 mm Adapter $3
2x 2 m Mono Patch Cable $4 each

Step 1: Get the VOX unit

I got mine from All Electronics. But there's a problem! The battery goes dead quickly, and is non-replaceable!
Voice Operated Xmit (Transmit). It's a term widely used in amateur radio and other telecom fields to denote a device that transmits, or turns on, after sound has crossed a certain threshold for volume. In other words, if you're not talking, it's not transmitting. If you are talking, it is transmitting. In this application, it's used to trigger a radio when data packets are coming from your computer, and to allow your computer to listen for data packets when it's not busy transmitting. Put another way, it's an automatic device for turning full duplex into half duplex so your sound card and radio can get along.
What's a VOX?

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Bio: I'm a physicist with a bunch of engineering experience, who likes to make stuff, and likes to get outdoors.
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