The MX105A is a monolithic CMOS tone detector for tone decoding in single and multitone signaling systems. Using phase locked loop (PLL) decoding techniques, the MX105A recognizes tones in the presence of high noise levels and strong adjacent channel tones. Detection frequency and bandwidth can each be independently adjusted. The design is immune to high levels of harmonic and sub-harmonic noise. It also maintains excellent noise immunity and constant bandwidth over a wide range of input signal levels. The MX105A requires a voltage supply of 2.7V to 5.5V and is available in the following package styles: 16-pin SOIC (MX105ADW), 16-pin PDIP (MX105AP), and 24-pin PLCC (MX105ALH).