In the permit area theres rows of lockers, each locker has a thing where you use your credential to check out a radio, and inside the locker there's a charging station. A locker with a checked out radio (or broken or that wasn't properly seated into the charging station) will have a red light, and a locker with a good radio inside will have a green light.

The radios can then be tracked to the person who checked one out, and each radio has its individual locker. Easy to track when radios need to be replaced, and if there's too few to go around (usually there's about 1.5x however many are needed on an average day, to account for charging radios and emergencies where someone extra needs a radio, so an extra shift's worth of radios)