pots

22 Articles

Dial-up Internet Using The Viking DLE-200B Telephone Line Simulator

November 19, 2024 by 26 Comments

Who doesn’t like dial-up internet? Even if those who survived the dial-up years are happy to be on broadband, and those who are still on dial-up wish that they weren’t, there’s definitely a nostalgic factor to the experience. Yet recreating the experience can be a hassle, with signing up for a dial-up ISP or jumping through many (POTS) hoops to get a dial-up server up and running. An easier way is demonstrated by [Minh Danh] with a Viking DLE-200B telephone line simulator in a recent blog post.

This little device does all the work of making two telephones (or modems) think that they’re communicating via a regular old POTS network. After picking up one of these puppies for a mere $5 at a flea market, [Minh Danh] tested it first with two landline phones to confirm that yes, you can call one phone from the other and hold a conversation. The next step was thus to connect two PCs via their modems, with the other side of the line receiving the ‘call’. In this case a Windows XP system was configured to be the dial-up server, passing through its internet connection via the modem.

With this done, a 33.6 kbps dial-up connection was successfully established on the client Windows XP system, with a blistering 3.8 kB/s download speed. The reason for 33.6 kbps is because the DLE-200B does not support 56K, and according to the manual doesn’t even support higher than 28.8 kbps, so even reaching these speeds was lucky.

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

November 2, 2024 by 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 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 End Of Landlines?

February 8, 2024 by 94 Comments

Imagine if, somehow, telephones of all kinds had not been invented. Then, this morning, someone entered a big corporation board room and said, “We’d like to string copper wire to every home and business in the country. We’ll get easements and put the wires on poles mostly. But some of them will go underground where we will dig tunnels. Oh, and we will do it in other countries, too, and connect them with giant undersea cables!” We imagine that executive would be looking for a job by lunchtime. Yet, we built that exact system and with far less tech than we have today. But cell phones have replaced the need for copper wire to go everywhere, and now AT&T is petitioning California to let them off the hook — no pun intended — for servicing landlines.

The use of cell phones has dramatically decreased the demand for the POTS or plain old telephone service. Even if you have wired service now, it is more likely fiber optic or, at least, an IP-based network connection that can handle VOIP.

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A Crossbar Telephone Switch Explained

February 4, 2024 by 14 Comments

There’s an old adage about waiting hours for a bus only for two to appear at once, and for Hackaday this month we’re pleased to have seen this in a run of analogue telephone projects. Latest among them is the video below the break from [Wim de Kinderen], who is demonstrating the workings of a mechanical crossbar switch with the help of a vintage Ericsson unit and an Arduino replacing the original’s bank of control relays.

It’s possible everyone has a hazy idea of a crossbar array, but it was fascinating from this video to learn that the relays are worked by metal fingers being inserted by the bars into relays with wider than normal gaps between electromagnet and armature. This extra metal provides a path for the magnetic flux to actuate the relay.

The machine itself then is an extremely simple and elegant electromechanical device with many fewer moving parts than its Strowger rotary equivalents, but surprisingly we seem to see less of it than its American competitor. The video below the break is definitely worth a watch, even if you don’t own any analogue phones.

We recently saw a similar exchange implemented electronically.

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A Complete Exchange From Scratch For Your Rotary Dial Phones

January 29, 2024 by 12 Comments

Such has been the success of the mobile phone that in many places they have removed the need for wired connections, for example where this is being written the old copper connection can only be made via an emulated phone line on an internet router. That doesn’t mean that wired phones are no longer of interest to a hardware hacker though, and many of us have at times experimented with these obsolete instruments. At the recent 37C3 event in Germany, [Hans Gelke] gave a talk on the analog exchange he’s created from scratch.

The basic form of the circuit is built around a crosspoint switch array, with interfaces for each line and a Raspberry Pi to control it all. But that simple description doesn’t fully express its awesomeness, rather than hooking up a set of off-the-shelf modules he’s designed everything himself from scratch. His subscriber line interface circuit uses a motor controller to generate the bell signal, his analogue splitter has an op-amp and a transistor, and his crosspoint array is a collection of JFETs. Having dabbled in these matters ourselves, it’s fascinating to see someone else making this work. Video below the break.

Have an analogue phone but nowhere to use it? Bring it to a hacker camp!

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POTS At A Hacker Camp

January 25, 2024 by 1 Comment

For those of us off the Atlantic coast of Europe it’s a frigid winter as our isles are lashed by continuous storms. Summer seems a very long time ago, and the fun of the EMF 2022 hacker camp is an extremely distant memory. But the EMF team have been slowly releasing videos from the talks at that camp, the latest of which comes from [Matthew Harrold]. He was the force behind the public POTS phone network at the camp, providing anyone within range of one of his endpoints with the chance to have a wired phone line in their tent.

We’d love to imagine a mesh of overhead wires converging on a Strowger mechanical exchange somewhere on the field, but in a more practical move he used an array of redundant Cisco VOIP gear, and a multi-modem rack to provide dial-up services. Even then there were a few hurdles to overcome, but on the field it was definitely worth it as an array of unusual phone kit was brought along by the attendees. Our favourite is the Amstrad eMailer, an all-in-one phone and internet appliance from a couple of decades ago which perhaps due to its expensive pay as you go model, failed commercially. The video is below the break.

It’s a good time for this talk to come out, because it’s reminded us that the next EMF camp is on this summer. Time to dust off an old phone to bring along. Meanwhile, we’ve seen [Matthew] before, as he refurbished a sluggish dial mechanism.

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