Paging networks in the UK use either POCSAG or FLEX protocols to transmit paging messages over the air to paging receivers. The POCSAG protocols can operate at three speeds, 512 bits per second, 1200 bits per second, or 2400 bits per second. Flex protocol speeds are higher and use four-level modulation techniques to achieve 1600 bits per second, 3200 bits per second and 6400 bits per second.
Each radio channel uses a narrow band 25KHz channel spacing that can support up to 50,000 uses representing a highly efficient use of the radio spectrum.