I will rely on information given by my husband, who has been in communications for over 30 years. A "keyed" microphone on a repeater system blocks other communications until the user releases.
Yes radios! That is what they use to communicate with. the same is true for police, fire, taxi, maritime vehicles and a host of others.
Ask your hubby if he knows what a first class commercial radio telephone operator’s license or an Extra class Amateur radio license is. I happen to hold both of those and have for probably more years than you have been alive.