Fax and Modem Bypass Mode

In this proprietary mode, when fax or modem signals are detected, the channel automatically switches from the current voice coder to a high bit-rate coder, according to the 'Fax/Modem Bypass Coder Type' parameter [FaxModemBypassCoderType]. The channel is also automatically reconfigured with the following fax / modem adaptations:

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Disables silence suppression

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Enables echo cancellation for fax

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Disables echo cancellation for modem

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Performs certain jitter buffering optimizations

The network packets generated and received during the bypass period are regular voice RTP packets (per the selected bypass coder), but with a different RTP payload type according to the following parameters:

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'Fax Bypass Payload Type' [FaxBypassPayloadType]

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[ModemBypassPayloadType]

During the bypass period, the coder uses the packing factor, configured by the 'Fax/Modem Bypass Packing Factor' parameter [FaxModemBypassM]. The packing factor determines the number of coder payloads (each the size of [FaxModemBypassBasicRTPPacketInterval]) that are used to generate a single fax/modem bypass packet. When fax/modem transmission ends, the reverse switching, from bypass coder to regular voice coder is performed.

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To configure fax / modem bypass mode:

1.

On the Fax/Modem/CID Settings page, do the following:

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Configure the 'Fax Transport Mode' parameter to Bypass [FaxTransportMode = 2].

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Configure the 'V.21 Modem Transport Type' parameter to Enable Bypass [V21ModemTransportType = 2].

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Configure the 'V.22 Modem Transport Type' parameter to Enable Bypass [V22ModemTransportType = 2].

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Configure the 'V.23 Modem Transport Type' parameter to Enable Bypass [V23ModemTransportType = 2].

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Configure the 'V.32 Modem Transport Type' parameter to Enable Bypass [V32ModemTransportType = 2].

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Configure the 'V.34 Modem Transport Type' parameter to Enable Bypass [V34ModemTransportType = 2].

2.

Configure the [BellModemTransportType] parameter to 2 (Bypass).

3.

Configure the following optional parameters:

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'Fax/Modem Bypass Coder Type' [FaxModemBypassCoderType]

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'Fax Bypass Payload Type' [FaxBypassPayloadType]

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[ModemBypassPayloadType]

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[FaxModemBypassBasicRTPPacketInterval]

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[FaxModemBypasDJBufMinDelay]