Polycom Vortex EF2241 Application Note page 8

Please follow our instructions for wiring the Vortex device to the codec. Failure to do so
may induce noise into the signals sent and received from the codec.
3. Raise the gain on the appropriate Input of the Vortex device to +10 dB.
4. Lower the gain on the appropriate Output of the Vortex device to -10 dB.
It is important to set the gain structure correctly so that you don't clip the input audio
stage of the codec and that the Vortex device gets a good signal to perform processing
with. The nominal input and output of the codec is .3 V rms. The nominal input and
output of the Vortex device is .775 V rms. This equates to a difference of 8.24 dB between
the two nominal levels. For simplicity, you may round that value to 10 dB.
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