The dulcet tones of a modem handshake may be a thing of the distant past for most of us, but that hasn’t stopped there being a lively hacking scene in the world of analogue telephones. Often that’s achieved using old devices resurrected from a parts bin, but sometimes, as with [Brian]’s USB modem, the devices are entirely new.
A surprise is that modem chips are still available, in this case the SkyWorks IsoModem chips. It uses an M.2 module format to allow the modem and support circuitry to be separated enough to place it in another project if necessary, along with a clear warning on the PCB not to put it in the identical-looking PC slot. It also comes with tips for experimenting if you don’t have access to a landline too, given that POTS is fast becoming a thing of the past itself in so many places.
If you’ve got nowhere to show off your modem, we’d like to suggest you try a hacker camp. There you’ll often find a copper network you’re positively expected to hack.
Here’s a cute Raspberry Pi hat modem, specifically designed to be used at hacker camps: https://x.com/AdiStuder/status/1800735915029221572
Github repo: https://github.com/astuder/ModemHAT
Cool! This brings back memories of another Raspberry Pi hat, btw.
It’s not a dial-up modem, but rather an emulation of it sort of.
It simulates an ancient DBT-03. I’ve read about the project a few years ago.
https://en.wikipedia.org/wiki/File:Modem_DBT-03.jpg
https://btx-museum.de/2020/02/15/ausblick-auf-den-neuen-dbt-03-adapter/
The project repo mentions that it’s very likely not legal to connect these to public POTS. Anyone know why or what makes it so?
In the UK, devices that connect to the public telephone network need to be approved. I suspect the same is the case elsewhere too, thinking back to all the different countries’ approval logos that used to be on stickers on modems. Presumably it’s as simple as these not having been approved for use anywhere that would make them illegal to use.
Missed opportunity to call it the “POTS Pi” 😁
Chicken!
:-)
I just want a small circuit to convert my old ringer Connairphone to IP phone and make it ring since new lines don’t send the necessary voltage to enable the ringer.
Take a look at the Grandstream HT801 (one line) or HT802 (2 lines). They will do exactly what you want (and support pulse or DTMF dial). Available on eBay fairly cheap, and there are cheaper Vonage-branded ones that are “locked” but there’s an unlock procedure on the web that worked for me.
i have an HT801 and it works very well with the relatively modern ‘trimline knockoff’ phone i got at the thrift shop. i’m surprised how easy it was to set up and how reliable it seems to be.
but i can’t help but wonder if it genuinely provides enough power for real ringing. i have no idea the numbers coming or going but it seems to me like the mechanical solenoid hitting a bell sort of ringer must draw a lot more current than the piezo ringer in this phone. i found a reddit post where reports were mixed — it sounds like it’s workable but you might have to futz with it.
Modem ? That’s great ! I still have 50 hours left on my AOL CD !