RXC-3000 Hardware Installation and User Guide
9000-0000-040 Revision 10 32 of 46 Genave Electronics
Two Tone Sequential Decoder
Two Tone Decoder Characteristics
The Two Tone decoder is a “Non-Predictive” decoder. This means that the decoder is not tuned to look
for a specific set of tones. Rather, the unit decodes tones it receives over-the-air and sends the tone
information to the main chip where they are compared to a list of tones attached to action scripts.
The Two Tone sequential decoder can detect tones between 210 Hz and 3000 Hz.
The decoder is equipped with an Auto-Correlator circuit that acts as a filter to remove background
noise from the audio presented to the decoder. Only signals that are periodic (tones) will be passed to
the decoder.
When decoding simultaneous multiple tones, the RXC-3000 will only pass along the data on the tone
with the greatest amplitude. Hence if the CTCSS or DCS tones are near or larger than a 1000 Hz tone
signal, the decoder chip will not pass data along about the 1000 Hz tone and since the CTCSS and DCS
tones are out of the range for the decoder, they are not decoded. The result is that the RXC-3000 does
not respond to the signal. As soon as the 1000 Hz signal is increased above the CTCSS or DCS tones,
the RXC-3000 will start to display the tone.
It is important to present the RXC-3000 with a clean RF and audio signal from the activation point. If
the audio signal is distorted as shown above, the unit will decode the signal, but due to the harmonics
riding on the signal, it may not correctly identify the frequency of the tone.
Illustration 1: Two Tone Sequential Tone Distortion
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