Digital Explained

a) FDMA stands for Frequency Division Multiple Access and is a channel access method used in one of the popular digital radio protocols, as per the illustration below :
b) TDMA stands for Time Division Multiple Access. TDMA is a multiplexing method that divides network connections into time slices, where each device on the TDMA network connection gets one or more time slices during which it can transmit or receive data, thus increasing the available channel usage. One of the big advantages of this is users can boost two channels using this protocol with a single two way radio Repeater or Talkthrough