The MX165C CTCSS Encoder/Decoder is a low voltage, CMOS device that meets TIA/EIA-603 Standards. The MX165C will encode and decode the tones 159.8Hz, 183.5Hz, 189.9Hz, 196.6Hz, 199.5Hz, 206.5Hz, 229.1Hz, and 254.1Hz in addition to the 39 standard CTCSS tones, for a total of 47 CTCSS tones + Notone. With the incorporation of the on-chip TX and RX speech filter, the MX165C enhances voice/tone multiplexing by attenuating TX and RX speech 36dB at frequencies below 250Hz while passing signals > 300Hz with only 1dB of ripple. This not only minimizes CTCSS talk-off in the TX mode but also improves Hum and Noise performance in the RX mode.