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Message-ID: <courier.00000000615A4BFA.000BBE54@coop.radagast.org> Date: 3 Oct 2021 17:34:02 -0700 From: "Dave Platt" <dplatt@radagast.org> Subject: Re: Can I send a FAX over a voip line? In theory, VOIP can carry fax transmissions, but in practice it does not work very well. You need to be using a simple codec (alaw or ulaw) and have very little timing jitter in your network path... otherwise there will probably be enough waveform distortion to corrupt the fax transmission badly. Other types of modem-over-VoIP have similar problems. Some VoIP providers have the ability to detect a fax handshake in an incoming call, terminate the call to a faxmodem, and forward the fax to you via email... and may provide an email-to-outbound-fax origination service as well.

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Message-ID: <20211004124943.98787.qmail@submit.iecc.com> Date: 4 Oct 2021 12:49:43 -0400 From: "bernieS" <bernies@remove-this.panix.com> Subject: Re: Can I send a FAX over a voip line? For 14 years I've been using RingCentral's email<>FAX gateway with success. It used to cost about $10/month if paid annually, but they've raised that considerably since (I'm grandfathered on the cost). Once subscribed, you can email many common document types as a file attachment to <faxnumber>@rcfax.com and they render it as a fax to the destination fax machine. Then a few minutes later they email you a confirmation that it was successfully received (or not.) Inbound faxes to your RingCentral fax number arrive as PDF's to your email inbox. It works pretty well. Years ago I setup an enterprise client with a similar service called Faxmail.com but they seem to have been bought out by a less friendly provider. Some email<>FAX gateway providers (like eFax, IIRC) require you to use their proprietary software and seem to monetize your traffic. I often use RingCentral FAX to exchange faxes containing patient medical info with medical service providers for myself and family members. I think HIPAA prohibits emailing such info, so most doctors seem to have a fax machine (or some kind of fax service) for compliance reasons. Ironically, because email<>FAX gateways use email as part of the path, using one for exchanging patient medical info probably violates HIPAA. FAX over VoIP -- can be done successfully depending on the CODEC that the VoIP provider uses. I recently discovered a FAX-friendly feature of Ooma is to prefix the outgoing fax call with *99 which invokes a FSK-friendly CODEC. I'm not sure if/how Ooma can be used to successfully receive faxes. Contacting your VoIP provider(s) higher-level tech support staff might yield useful info, such as any dialed prefix with invokes a FSK-friendly CODEC for that outbound call. I had to talk with several Tier III tech support staffers at Ooma to reach a someone who knowledgeable about this. I don't think there's any legal requirement that VoIP providers such as Callcentric support such a capability. But obviously, the slower the fax/modem connection speed (bits per second) the more reliable the transmission will be. Some older Group III fax machines have modems that can negotiate all the way down to 300 bps, which would wonk better over some VoIP connections. YMMV. -bernieS

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Message-ID: <sje50j$qs7$1@shakotay.alphanet.ch> Date: 4 Oct 2021 05:55:31 -0000 From: "Marc SCHAEFER" <schaefer@alphanet.ch> Subject: Re: Can I send a FAX over a voip line? Bill Horne <telecomdigestsubmissions@remove-this.remove-this.telecom-digest.org> wrote: > I have a vague memory of some requirement that VoIP phone lines support > FAX transmission. I'd like that to be true, but before I go to the > effort of getting my VoIP->POTS adapter to work with Callcentric, I'd > appreciate your help. It will be slow and unreliable to transmit fax audio through Voice-over-IP. However, most VoIP adapters have a T.38 settings, and if this supported by your Voice-over-IP provider, it will work [1]: the fax will not be sent through audio but numerically: without T.38, slow, unreliable: fax machine --- VoIP adapter --- Internet --- VoIP provider analog numeric audio audio numeric audio with T.38, fast, reliable: fax machine --- VoIP adapter --- Internet --- VoIP provider analog T.38 data audio T.38 data After the VoIP provider, you get a standard phone network capable of handling fax audio, where T.38 is converted back. But more problems might happen if the other end is also VoIP without T.38. Another alternative would be to sign up with an e-mail to/from fax service provider, there the fax is sent or received as a compressed image. [1] https://www.callcentric.com/faq/30#205 seems to support receiving fax to e-mail, and has information about T.38 and no T.38.