Particularly on spacewalks, I notice that the transmissions from the astronauts are often choppy, and they have that sound of voice-activated mikes. But that causes some cutoff of the beginning and end of their various statements, questions, etc. and occasional breakups. Why don’t they just keep the microphones open? Also, does anyone know of a good site that lists some of the gazillion acronyms they use?
I just thought of one - it takes less electricity. Is that the main reason?
With VOX you don’t have to take a hand off what you are doing to key the mike.
IIRC, this is how we got ‘A-OK’. The ‘A’ was to open the VOX mic.
Many of the acronyms are known by the TLA “TLA” which means “three letter acronym”
Wikipedia’s page on TLA has some examples, but no link like “TLAs used by NASA” that I can find.
Not necessarily the reason they don’t use it, but an open mike is annoying, it picks up all your breathing and so on, much nicer to have your intercom quiet until you want to say something.
It may be to maintain compatibility with the analog UHF radio system that is the backup for the digital TDM voice communications system.
“Look Ma. No hands!”
It keeps extraneous background noise to a minimum.
Imagine several open mikes in a noisy area. Result would be neigh impossible communications.
When working with CG helo pilots, they’d begin every transmission with a drawn out “And…”. I always assumed this was to activate the VOX.
As to the OP - you may find some of the acronyms here: www.acronymfinder.com
Had a teacher in high school who flew B-52 bombers for the Air Force. He said the intercom that the aircrew used to talk to eachother was a “hot mike” (ie: allways open) so when the pilot was executing some particularly difficult maneuver, everyone on the plane could hear his heavy breathing, low-volume swearing, etc.
Plus, if you have more than one person on the same radio frequency, then keeping the channels open all the time can cause them to jam eachother, I would assume.
Could he use a coffee and a blowjob?
The helicopters I’ve flown have button-activated intercoms. (I’m not in the Coast Guard – I’m talking Robinsons and Schweizers.) The fixed-wing aircraft with intercoms I’ve flown have had VOX-activated intercoms. (Both have PTT radios.)
With the fixed-wing intercoms, I found myself starting with ‘Uh…’ 
Well, yes. If it is a closed circuit intercom then people can speak at once (like on a telephone), but if it is transmitted over a radio frequency then you can’t have any open mics as they jam the frequency.
Heh, when I took my Private Pilot Ground School courses in high school, our instructor stressed that people who came on the radio with “Uhhh…” were some of the more annoying things you encountered in the air. 
I only did it on ythe intercom. Never really heard people drawl on the radio.