The Local Application Control Bus System (LANC) is the protocol used by Sony camcorders (and some other brands as well) that allows external accessories to control the camera remotely. On most cameras, you’ll find a LANC port next to your camera’s other IO jacks—it’s usually a 2.5mm headphone-style jack, or a 5 pin mini-DIN.
If you’re an Arduino fan, you can easily create your own custom devices that can interact with your camcorder using the LANC protocol, allowing you to control zoom and record functions from your own programs. Goose wrote about his own project and example Arduino source:
I found source code to do LANC control with the Arduino board. It was written quite well – it worked the first time out. I made a few changes though, specifically changing it from being controlled by a serial port to being controlled by a potentiometer. I plan to build my own zoom controller with it, using an Arduino Mini.
The original code comes from Brady Marks. Make sure to check out the README and other documentation inside the source zip file. Along with the Arduino source, there’s a bunch of LANC protocol documentation as well as some collected emails and mailing list discussion on the topic.