Apple USB Modem and VoIP

Question

Level 2

157 points

Apple USB Modem and VoIP

I've been trying to help a friend set-up an Apple USB modem with his MacBook Pro. He wants to have it as a back-up, in case he is somewhere without any other form of Internet access. I've been using Macs for a long time and thought this would be a no-brainer, but it hasn't. I get a dial-tone, I hear the attempted connection sounds, then nothing - "dial tone not detected", or something like that. Earthlink confirmed that the access numbers were correct, plus the phone works fine. I've tried 2 different USB modems. I realized that he is using VoIP for his home phone and that the line runs through a Linksys "Viatalk" router. Could that be the cause of the problem? Are modems "supposed" to work over VoIP systems?

TIA

iMac G5, Mac OS X (10.5.5)

Posted on Oct 6, 2008 9:01 AM

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Answer 1

Camelot

Level 9

58,575 points

Oct 6, 2008 11:38 AM in response to Rob J

due to the various encoding and compression algorithms used, you typically cannot use a modem (including the modem built into fax machines) on most VoIP lines.

The VoIP connection is optimized to carry voice traffic and doesn't support the full signal range needed by modem communications.

You might try asking your VoIP provider for some assistance - some offer fax modem lines which may support modem transfers.

On the plus side I trust you are using this for testing only, right?
There's no point in using a modem as backup in case your main internet connection goes down because if your main line goes down, so does your VoIP connection - therefore you couldn't use the VoIP connection anyway.

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Answer 2

Rob J Author

Level 2

157 points

Oct 6, 2008 2:23 PM in response to Camelot

Thank you, I had a feeling that was the case. Yes, I was just using it for testing. My friend occasionally finds himself in remote locations that don't have any WiFi or broadband access and wanted to make sure the modem worked and was configured correctly.

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Answer 3

Tim Haigh

Level 7

24,198 points

Oct 10, 2008 3:34 AM in response to Rob J

Most good quality codecs for VOIP require 10k of bandwith in and out something a dial up modem does not have.

For a portable solution you may want to consider a usb 3G/hsdpa adapter. Please note that some providers prohibit the use of VOIP on these connection unless you pay for a business/high end tarrif.

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