can't send fax via EVM-HD 8FXS/DID

Answered Question
Aug 20th, 2010
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Hello All,

I use EVM-HD 8FXS/DID on ISR 3825  and analog fax (connected to fxs port on EVM-HD 8FXS/DID).

From fax I can make a call to PSTN and have connection without problems with another customer of PSTN. But if I call to fax, I hear a fax from the other side just during 1...2 seconds and then I get a silence and can't send a fax (my fax machine tells that it "has no connection or response").

Can you give me a hint how to solve the issue

Correct Answer by paolo bevilacqua about 6 years 9 months ago

Configure


network-clock-select 1 e1 0/2/0

voice service voip

fax protocol none



and try again.

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paolo bevilacqua Fri, 08/20/2010 - 08:24
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Which type of access you have to PSTN ?

Config ?

Christopher Graham Fri, 08/20/2010 - 15:09
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If this is a pots to pots fax (FXS on the inside, PRI or FXO on the PSTN side), I have seen instances where the volume out to the PSTN was too low, or volume inbound was too high.  This can cause one side to not recognize the other as a fax transmission and drop the call.  Try playing with the input gain/output attenuation on one of the pots legs.


Have you tried faxing inbound?  Does that work?


Otherwise, we need to see the config, and need to know that complete call flow.  Is the fxs port mgcp controlled?  Are you doing H323/SIP to CUCM and hairpinning back to the gateway and out the PSTN? 

Correct Answer
paolo bevilacqua Sat, 08/21/2010 - 02:39
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Configure


network-clock-select 1 e1 0/2/0

voice service voip

fax protocol none



and try again.

Andrey128 Sat, 08/21/2010 - 03:37
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Yes, now it's working!

And have two questions:

- will "fax protocol none"  be  an issue if our ISR 3825 is also used for onramp fax?

- after sending a fax instead of "busy" signals I hear just a silence, how to allow "busy" signals after a fax was sended?

paolo bevilacqua Sat, 08/21/2010 - 05:06
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1. no, it doesn't affect T.37

2. take "debug isdn q931" with "term mon". If you do not receve disconnect after the fax is sent, then no signal can be heard. However, fax operation never depends by busy signal.


Thanks for the nice rating and good luck.

Andrey128 Sat, 08/21/2010 - 01:30
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Hi All!


ISR 3825 is connected to PSTN via PRI controller E1 port 0/2/0 (VWIC 2MFT-E1-DI). Analog fax machine is connected directly to fxs port voice-port 2/0/0 on EVM-HD 8FXS/DID


Config according to this task:




voice service voip
fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback none
sip
!
controller E1 0/2/0
framing NO-CRC4
pri-group timeslots 1-12,16
!
interface Serial0/2/0:15
no ip address
encapsulation hdlc
isdn switch-type primary-net5
isdn protocol-emulate network
isdn incoming-voice voice
isdn sending-complete
no cdp enable
!
voice-port 0/2/0:15
!
voice-port 2/0/0
caller-id enable
!
voice-port 2/0/1
!
voice-port 2/0/2
!
voice-port 2/0/3
!
voice-port 2/0/4
!
voice-port 2/0/5
!
voice-port 2/0/6
!
voice-port 2/0/7
!
dial-peer voice 44 pots
destination-pattern ..........
incoming called-number ..........
direct-inward-dial
port 0/2/0:15
!



For fax on  EVM-HD 8FXS/DID I created one dial peer (which is in config) and checked that it matches numbers which I dial for testing.
We don't use mgcp and we don't use H323/SIP to PBX in this situation.

I also tried to change gain on the call legs:


or EVM-HD 8FXS port:
(config)#voice-port 2/0/0
(config-voiceport)#input gain 7
(config-voiceport)#output attenuation 10
 
for outbound call leg:
(config)#voice-port 0/2/0:15
(config-voiceport)#input gain 7
(config-voiceport)#output attenuation 10


after that I hear fax during 1...2 seconds and than periodical peeps,

when I set gain to 9 for both call legs I have a problem with digit identification by ccme

do recommended values of gain and attenuation exist?



inside a network faxes were trinsmited successfuly

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