The FX828 is an innovative CTCSS, DCS and Selcall Codec, designed for the latest generation of Land Mobile Radio equipment. Designed to complement the FX829, the FX828 has many advanced features which assist the operation of modern SUBAUDIO and INBAND based signalling systems. The FX828 is electrically, physically and software compatible with the FX818 and FX829. It permits manufacturers to add new features to their equipment with minimal design changes. The FX828 incorporates a programmable tone decoder which can be set to respond to between 1 and 15 CTCSS or Selcall tones with minimum software intervention. In addition, a 'Fast' CTCSS detector can respond to a single programmed tone in 60 ms, or can be used to provide an output if any CTCSS tone is present at the detector input. Two high resolution tone encoders perform accurate generation of any CTCSS or Selcall tone in current use. Full 23 or 24 bit DCS encoding and decoding complements the CTCSS/Selcall line-up. A timer is included which, for example, may be used for timing Selcall transmissions and a comparator is provided to assist with carrier or RSSI monitoring. The device can operate full duplex in all operating modes except for DCS.