in older analog intercom systems, each beltpack, as well as the base station, had their own individual frequencies. This was easy to engineer, but very spectrally inefficient and very susceptible to interference and multipath fading. By using TDMA, the base station and all of its associated beltpacks operate on the same frequency at any given time. This is called multiple remote access. All of the devices on the RF link share, or multiplex, the frequency. First, the base station “says” what it has to say to each beltpack, while all of the beltpacks “listen”. Then, each beltpack in turn “talks” back to the base station with its own information. Once all of this occurs, the whole system changes frequencies and it happens all over again.