Land Mobile Radio System

When the LMR radio operates in digital mode, the carrier is moved to four specific frequency offsets that represent four different two-bit combinations. This is a modifi ed 4 level FSK used in analog radio systems. In analog mode, the LMR radio will operate exactly the same as conventional analog systems, with the capability for CTCSS, DCS, pre-emphasis and de-emphasis, wideband or narrowband operation and other standard analog features.In digital mode, the LMR transmitter will convert all analog audio to packets of digital information by using an IMBE vocoder, then de-vocode the digital information back to analog audio in the receiver.
Error correction coding is added to the digital voice information as well as other digital information. Analog CTCSS and DCS are replaced by digital NAC codes (as well as TGID, Source and Destination codes for
selective calling). Encryption information can be added to protect the voice information, and other digital information can also be transmitted such as a user defi ned low speed data word or an emergency bit.The following section provides an overview of the range of applications in which Daniels Radio equipment can be used. Both Digital (P25) and analog applications are covered including:


Repeaters

Land Mobile Radio (LMR) operate in a similar manner to conventional analog FM radios. LMR radios will operate in conventional analog mode, making them backwards compatible with existing analog radio systems.