I've got the same problem with my cops and forest rangers. I'm calling them hand-helds. Geeze, I've the National Guard out there and I say they're using field phones. Hope I'm right. Close only counts in horseshoes.
Tri
Tri,
The answer depends on when your story is set. However, if it's fairly modern, the below answer should help.
Field Phones (TA-312s) are actual phones linked together by wire, sometimes through a switchboard, but usually point to point. Those are primarily used when the situation is static as it provides good security, but they're a bear to use as someone (called a line doggie) has to run the telephone wire(s) from Point A to Point B (hoping people don't trip over it, run over it with a vehicle, etc). Once it's in place, it's just turn a crank to generate some electricity and hit the ring button.
If it's modern National Guard, they're using SINGARS radios (frequency hopping radios) that have been synched together. The Army got rid of the old VRC-46 single-channel VHF radios back in the early 90s and the NG probably got rid of theirs in the mid-90s as stuff filtered down to them.
If you have specific questions, give me a buzz. I was one of the main troubleshooters for my platoon's radios from 1989-1994.