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Technical
Support - Hardware
FAX & ATA186 Documentation
 Using
the FAX Passthrough Feature
Both ports of the Cisco ATA 186 support FAX
transmission. The Cisco ATA 186 can send FAXes by either of
two methods:
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FAX passthrough—In this mode, the
Cisco ATA 186 can detect a FAX tone, after which it will
turn off FAX tone detection and silence suppression and
switch its operating codec to G.711 u-law or G.711 A-law.
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G.711 FAX mode—In this mode, the Cisco
ATA 186 simply passes the RTP packets sent between the
end FAX machines without any intervention. It treats the
FAX session like any normal voice call.
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About
FAX Passthrough
To use the FAX passthrough feature, both the Cisco ATA 186 and
the supporting gateway must be configured at both ends to detect
the FAX tone and switch codec.
The Cisco ATA 186 supports two G.711 upspeed methods for FAX
passthrough:
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The Cisco proprietary codec switch
using NSE packets and RTP detection.
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The standard-based protocol level
(H.323/SIP) codec switch.
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To interoperate with a Cisco gateway, which
does not send protocol level codec switch requests but can accept
them, select the Cisco proprietary codec switch.
Configuring the Cisco ATA 186 for FAX Passthrough
There are two possible modes of configuration,
ConnectMode and AudioMode.
ConnectMode
The ConnectMode bits in the Cisco ATA 186 configuration control
the functions described below. To interoperate with a Cisco
gateway, Cisco recommends you set the bits as follows:
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Bit 7 (mask 0x80)—1 means enable FAX
passthrough redundancy; 0 means disable.
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Bits 8-12 (mask 0x1F00)—Offset to
NSE payload-type number 96. The default value is 4 (as
NSE payload-type number 100), and the valid values are
2 to 23 (98 to 119).
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Bit 13 (mask 0x2000)—0 means use G.711u-law;
1 means using G.711A-law as the new codec.
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Bits 14, 15 (mask 0xC000)—Set as 00
to enable the FAX passthrough feature using the Cisco
proprietary method (recommended). Set as 11 to disable
FAX passthrough.
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For example, a example, a *ConnectMode* setting
of 0xXXXX040X means use NSE payload-type number 100, G.711u-law
codec, and no redundancy in FAX passthrough mode.
AudioMode
Set to 0xXXXX0015 for line 1, or 0x0015XXXX for line 2, (X=don't
care). This setting enables FAX tone detection.
Disabling
the FAX Passthrough Feature
To disable FAX passthrough, turn on bits 14
and 15 of the ConnectMode in the Cisco ATA 186 configuration.
On the Cisco gateway, enter:
no modem passthrough
About FAX Mode
Some users might want to set one or both lines
of the Cisco ATA 186 to pure G.711 FAX mode. This mode allows
the FAX machine connected to the Cisco ATA 186 to communicate
directly with the FAX machine at the other end of the call with
no FAX signaling events between the two FAX machines. |
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