SIP Alias to Fax machine issue

[Anonymous]

After upgrading to R10.8.1.E we are having a problem with incoming faxes.  The phone number is an SIP alias from our SIP provider.  The FAX machine is hooked to FXS 2/4.  If I put an analog phone on the the FXS port, the phone does ring, but the FAX machine does not pickup.  Is there some option or feature that I need to set on this User Account so that the FAX machine will detect the call?

Here is the user config:

Nettech_NV7100#show running-config voice user 394
Building configuration...
!
!
!
voice user 394
  connect fxs 2/4
  cos "normal_users"
  first-name "Fax"
  last-name "Nettech-Main"
  password "1234"
  no call-waiting
  no fwd-courtesy
  no special-ring-cadences
  no message-waiting
  num-rings 6
  sip-identity 8148365228 T05
  sip-authentication password "1234"
  modem-passthrough detection-time 0
  t38
  no alc
  no nls
  no echo-cancellation
  codec-list g711_first
  no voicemail new-user
  voicemail auth-mode password
  no voicemail auto-play
  no voicemail envelope-play
  voicemail password "1234"
  voicemail notify schedule Sunday 12:00 am
!
!
end

[Anonymous · Accepted solution]

First thing is try changing the Detection Timespan from 0 to 8 seconds. The default should be 8, so not sure why yours it set to 0.

If that doesn’t work, then you might want to disable Modem Passthrough and manually set up the port to receive a fax.

Create a G.711ulaw only codec list and assign it to the interface and then make sure VAD and Echo Cancellation are turned off.

That should take care of it. Post back was fixed it.

More info on those settings;

Modem Passthrough

When Modem Passthrough is enabled and an existing call detects a modem or fax tone, the

unit will automatically renegotiate with the far end to be modem-compatible (switch to

G.711 codec automatically, echo cancellation and VAD are disabled). When connecting

analog port to a fire alarm system, DO NOT use modem passthrough. Manually assign a

G711 only codec, then disable VAD and echo cancellation.

Detection Timespan

Specifies the fax and/or modem detection time length value. Recommend starting with 8

seconds. Range is 0-8 Seconds

-Mark

[Anonymous]

Mark,

Those settings were a carry over from the original pre-R10.5.3 config.  After adjusting those settings and rebooting the fax machine, everything appears to be working normally.  Thanks

Jim