Yes, G711 (clear channel) is the only voice codec which you can use to send a FAX. The G729 codec compresses the audio stream by removing all inaudible frequencies, which FAX machines use, and so a FAX over G729 will always fail.

Darren Nay

-----Original Message----- From: Ronald Ramos [mailto:ron@silverbackasp.com] Sent: Friday, October 29, 2004 9:03 AM To: serusers@lists.iptel.org Cc: asterisk-users@lists.digium.com Subject: [Serusers] Grandstream HT486 and FAX

Hi All,

I was trying to test to send a fax to an international number. Here's the setup:

FAX --> HT486 --> SIP PROXY --> GATEWAY --> PSTN --> FAX

Unfortunately I haven't been able to do it, I read somewhere that fax uses G711 only, is this true? because our gateway provider uses only G729. does this mean I can't send fax via that gateway, because of the codec?

So can i do this then,

FAX --> HT486 --> SIP PROXY --> HT486 --> FAX

i'll use G711 on both HT486.

Hope anyone can help me. Thanks in advanced.

Regards, Ron

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