In my experience VoIP lines don’t like anything over 9600. Anecdotally, I’ve heard a call to the provider to request a tweak to allow faster speeds sometimes works. On Tue, Nov 7, 2023 at 5:43 PM Stephen A Edwards via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
I'm trying to get a computer device c. 1999 to "phone home": it includes a relatively fast voiceband modem (I'm not sure of the exact speed) that needs to be connected to a POTS landline (i.e., RJ-11). It's not a fax modem, but it's playing at least as many tricks as a fax modem.
I've currently tried about 6 different variants of VoIP/cable modems and they all don't work to varying degrees. I've tried seemingly every setting (codec -- I'm using the recommended G117u, jitter control, RTP packet size, echo cancellation off, etc.) on a Cisco SPA112 ATA I borrowed and it connects for a minute or two before giving up: the best behavior I've observed.
I'm convinced that it won't work without connection to a traditional landline, i.e., that's connected to the PSTN through a T1 or equivalent circuit-switched, synchronous connection.
Is there anybody in the New York City/New Jersey area who has an old-school landline (i.e., not from a cable modem or equivalent) that I could experiment with for an hour or so? Contact me off-list