The Alliance Comm System is voice-activated and context-aware. It responds to certain commands issued to it when the individual using it taps the comm button or verbally addresses the Comm System. To see an example of how it works in a real-world setting, imagine that we have two individuals on a planet's surface. These two men, Jones and Davis, are searching for minerals needed on the ship to complete a repair. Jones and Davis are friends. Davis is married, and has recently had an argument with his wife. Jones is concerned about both of them. He and Davis are separated from one another on the planet's surface as this conversation begins.
"Jones to Davis. Have you found any yet?"
"Nah. Let's keep looking. Privately to Davis onboard the ship."
"Hi Carl. Is everything OK down there?"
"Yeah. I just wondered if Tom apologized to you about last night. He was really out of line with you, Janet."
"We're fine, Carl. Tom and I talked it over this morning."
"Glad to hear it. Jones to Tom Davis. Hey, I found something. Jones to Davis onboard, I've gotta go. I just found the mineral. Jones to Davis on surface. I found some."This (very white room) exchange shows how the Comm System is used. When Carl Jones issued the command "Jones to Davis" the Comm System recognized that Jones wanted to open a two-way communication with Davis - in this case, the closest Davis to him, which was Tom Davis in his landing party. Later, when Jones says "Privately to Davis onboard the ship" the Comm System knew that Jones wanted to talk to the other Davis, Janet, back on the ship. It opened the communication with the ship and connected Carl to Janet, and since Carl specified that this was a private communication, Tom didn't hear the command or know about the communication between his wife and friend.
There's more to the Alliance Comm System design than this, but you probably get the gist of it from this little example. Characters can "conference call" over the comm system, send private messages between one another, add or remove people from the conversation, etc.