The CMX813 decodes the signalling tones for the Motorola Quick Call series, GE groups A, B and C and the tonesets employed by the Zetron, Reach and Plectron 2-tone radio paging systems. It also decodes the tones for Motorola 5/6-tone paging and the EIA, CCIR, ZVEI1 and EEA tonesets used for HSC radio paging and SELCALL. A simple serial interface allows the host C to specify the individual tone(s), or group of tones, to be decoded from the extensive list held by the CMX813. When the C receives an IRQN it examines the STATUS and DECODED TONE ADDRESS Registers to reveal the tone decoded. In 2-tone mode, the CMX813 will report which of the (up to eight) selected tones it has decoded. This report is an 8-bit index number to the tone in the programmed list. For 5/6-tone or HSC groups, the CMX813 will report which tone in the selected system toneset (eg CCIR, EIA) has been decoded, as a 4-bit hexadecimal tone value within the selected group. To allow for cadence measurements, the IRQN is activated again when the tone is no longer present. A status value of "No-tone" is returned. The CMX813 is designed to operate over a wide temperature range with a typical operating current of 0.5mA at 2.7Volts. It also has a Zero-Power mode and is available in TSSOP (E4) and DIL (P3) packages.