A Modem As A Cassette Interface

January 24, 2025 by Jenny List 20 Comments

At least some in the audience will at some time in the distant past have loaded or saved a program on cassette, with an 8-bit home computer. The machine would encode binary as a series of tones which could be recorded to the tape and then later retrieved. If you consider the last sentence you’ll quickly realize that it’s not too far away from what a modem does, so can a modem record to cassette and decode it back afterwards? [Jesse T] set out to give it a try, and as it turns out, yes you can.

The modem talks and listens to the cassette recorder via circuitry that provides some signal conditioning and amplification, as well as making a dial tone such that the modem thinks it’s talking to a real phone line. An Arduino steps in as dial tone creator.

Of course, this is hardly a viable solution to 21st century data storage need, but that’s hardly the point as it’s a cool hack. We like it, and oddly we’ve seen a similar technique used with a retrocomputer in the past.

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A Quarter And A Dime Will Get You A Commodore 64 Softmodem

January 20, 2025 by Lewin Day 43 Comments

Back in the 1980s, a viable modem cost hundreds of dollars. Even in the 1990s, you were looking at spending a a Benjamin or two to get computer squawking down the phone lines. According to [Cameron Kaiser], though, it’s possible to whip up a softmodem using a Commodore 64 for much cheaper than that. How much? Just 35 cents, we’re told!

The inspiration was simple—Rockwell apparently used to build modems using the 6502. The Commodore 64 has a 6502 inside, pretty much, so surely it could be a softmodem, right? Indeed, one [John Iannetta] had done this in a one-way form in the 1980s, using the Commodore 64’s SID audio chip to output data in sound form. In 1998, he espoused the 35-cent modem—basically, the price of buying an RCA jack to hook up a phone line to your Commodore 64.

As [Cameron] found out, the concept still works today, as does [John’s] code, but it’s more like 68 cents in 2025 dollars. With the right bits and pieces, and a little code, you can have your C64 modulating data into sound at rates of 300 baud.

It’s hacky, slow, and there’s no real way to receive—the C64 just doesn’t have the chops to demodulate these kinds of signals on its own. You also shouldn’t use it on a real phone line if you don’t want to damage your C64. Still, it’s a wonderful bit of hackery, and it’s fun to see how well it works. We’ve seen some other great Commodore 64 modem projects before, like the ever-useful RetroModem. Meanwhile, if you’ve got your own communication hacks for the computers of yesteryear, don’t hesitate to let us know!

Getting Dial-Up To Work Over VOIP Isn’t Always Easy

December 19, 2024 by Lewin Day 26 Comments

Dial-up modems used to be the default way of accessing the Internet, but times have moved on. They’re now largely esoteric relics from a time gone by. With regular old phone lines rather hard to come by these days, [Peter Mount] decided to try getting a pair of dial-up modems working over VoIP instead.

The build started with a pair of Linksys PAP2T VoIP phone adapters, which were originally designed for hooking regular phones up to VoIP systems. He paired each US Robotics modem with a PAP2T, and then hooked both into a VoIP Private Branch Exchange which he set up using 3cx on a Raspberry Pi 3B+. The Pi also acted as a server for the modems to connect to. It took a lot of fiddly configuration steps, but he found success in the end. On YouTube, he demonstrates the setup—with that glorious modem sound—communicating successfully at a rate of 9600 baud.

It’s nice to see this vintage hardware communicating in a what is effectively a simulated world created entirely within modern hardware. We’ve seen similar projects before, like this attempt to get dial-up going over Discord. If you’re doing your own odd-ball screechy communications experiments, don’t hesitate to drop us a line!

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The Tsushin Booster – A PC Engine Modem Add-on With A Twist

November 2, 2024 by Dave Rowntree 5 Comments

Sometimes, hardware projects get cancelled before they have a chance to make an impact, often due to politics or poor economic judgment. The Tsushin Booster for the PC Engine is one such project, possibly the victim of vicious commercial games between the leading Japanese console manufacturers at the tail end of the 1980s. It seems like a rather unlikely product: a modem attachment for a games console with an added 32 KB of battery-backed SRAM. In addition to the bolt-on unit, a dedicated software suite was provided on an EPROM-based removable cartridge, complete with a BASIC interpreter and a collection of graphical editor tools for game creation.

Internally, the Tsushin booster holds no surprises, with the expected POTS interfacing components tied to an OKI M6826L modem chip, the SRAM device, and what looks like a custom ASIC for the bus interfacing.

It was, however, very slow, topping out at only 1200 Baud, which, even for the period, coupled with pay-by-minute telephone charges, would be a hard sell. The provided software was clearly intended to inspire would-be games programmers, with a complete-looking BASIC dialect, a comms program, a basic sprite editor with support for animation and even a map editor. We think inputting BASIC code via a gamepad would get old fast, but it would work a little better for graphical editing.

PC Engine hacks are thin pickings around these parts, but to understand a little more about the ‘console wars’ of the early 1990s, look no further than this in-depth architectural study. If you’d like to get into the modem scene but lack original hardware, your needs could be satisfied with openmodem. Of course, once you’ve got the hardware sorted, you need some to connect to. How about creating your very own dial-up ISP?

A Brand New USB Modem In The 2020s

September 17, 2024 by Jenny List 11 Comments

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.

The JawnCon 0x1 Badge Dials Up A Simpler Time

September 16, 2024 by Tom Nardi 10 Comments

For hackers of a certain age, the warbling of an analog modem remains something of a siren song. Even if you haven’t heard it in decades, the shrill tones and crunchy static are like a time machine that brings back memories of a bygone era. Alien to modern ears, in the 1980s and 90s, it was the harbinger of unlimited possibilities. An audible reminder that you were about to cross the threshold into cyberspace.

If you can still faintly hear those strangely comforting screeches in the back of your mind, the JawnCon 0x1 badge is for you. With a row of authentic vintage red LEDs and an impeccably designed 3D-printed enclosure, the badge is essentially a scaled-down replica of the Hayes SmartModem. But it doesn’t just look the part — powered by the ESP8266 and the open source RetroWiFiModem project, the badge will allow attendees to connect their modern computers to services from the early Internet via era-appropriate AT commands while they’re at the con.

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Pulling Apart An Old Satellite Truck Tracker

September 13, 2024 by Lewin Day 9 Comments

Sometimes there’s nothing more rewarding than pulling apart an old piece of hardware of mysterious origin. [saveitforparts] does just that, and recently came across a curious satellite system from a surplus store. What else could he do, other than tear it down and try to get it humming?

The device appeared to be satellite communication device for a tracking unit of some sort, complete with a long, thick proprietary cable. That led to a junction box with a serial port and an RJ45 port, along with some other interfaces. Disassembly of the unit revealed it contained a great deal of smarts onboard, including some kind of single-board computer. Comms-wise, it featured a cellular GPRS interface as well as an Orbcomm satellite modem. It also packed in GPS, WiFi, Xbee, Ethernet, and serial interfaces. It ultimately turned out to be a Digi ConnectPort X5 device, used as a satellite tracking system for commercial trucks.

What’s cool is that the video doesn’t just cover pulling it apart. It also dives into communicating with the unit. [saveitforparts] was able to power it up and, using the manufacturer’s software, actually talk to the device. He even found the web interface and tested the satellite modem.

Ultimately, this is the kind of obscure industry hardware that most of us would never come into contact with during our regular lives. It’s neat when these things show up on the secondary market so hackers can pull them apart and see what makes them tick. Video after the break.

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