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would only pass through Headers which start with X- or Remote.
Other config options
dgain_packet_to_pcm
Sets the Volume level in the direction IP to TDM, valid values are "-14.0 to +6.0 dB (range -140 to +60)"
Default is 0
dgain_pcm_to_packet
Sets the Volume level in the direction TDM to IP, valid values are "-14.0 to +6.0 dB (range -140 to +60)"
Default is 0
ec
Enables or disables the configured echo canceller on voice channels, can be 0 (disable echo canceller) or 1 (use echo canceller).
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