Dial-up Internet access in 2024 using the Viking DLE-200B telephone line simulator

I got to know the Internet in secondary school, using a 33.6Kbps US Robotics dial-up modem on my Pentium I desktop running Windows 98. Despite the painfully slow connection (though fast enough for the time), I discovered many new things that sparked my interest in software development—things I wouldn’t have been able to learn through traditional methods. I continued to use that modem for Internet access until the early 2000s, when I got my first ADSL connection. The old dial-up modem was eventually recycled, and I hadn’t used dial-up again until recently, aside from a brief experiment a few years ago. That experiment involved using dial-up through a circuit-switched data connection, with a mobile phone acting as a modem for a Windows computer. The 9600bps CSD connection was much slower than traditional dial-up over POTS, but it was enough to reignite my interest in dial-up and make me appreciate how far technology has advanced.

Earlier this year I bought a Vikings DLE-200B Telephone Line Simulator for a mere $5 from a local flea market. This product simulates a traditional telephone line between two analog phones, allowing you to use them for intercom-like communication within the house without a landline connection. What I like most about the DLE-200B is its simplicity, with only two RJ-11 ports and a set of DIP switches to configure various ring settings at the back – there is no need to install any software or visit any web portal for configuration. The ‘BUSY’ LED, located on the left of the DIP switches, will light up if either phone is off the hook.

Looking from the front, the Viking is just a rectangular box with a socket for an AC power adapter:

The official power adapter is rated for 120VAC 60Hz and outputs 13.8VAC. I doubt the AC input needs to be 60Hz or the output needs to be exactly 13.8VAC, for the unit works fine when connected to a transformer stepping down from 220VAC @ 50Hz to 110V. Anything between 12V-15VAC should be good enough. As to why the power adapter outputs AC and not DC, well, if you cannot answer that question, then you should not be playing with dial-up in 2024! Simply put, the ring voltage on an analog telephone line is AC, and having the power adapter outputting AC will just be more convenient for the circuit designer. This is the official power adapter:

This is the bottom of the Viking:

To test the unit, connect two analog phones to the RJ11 ports. Pick up the headset on one phone and the other phone will just ring (after around 2-3 seconds of US-style dial-tone) with the RMS voltage measured around 80VAC. Ringback tone (US style with single beep for each ringback) will also be played. Relay clicks from the Viking can also be heard as the phone rings. Answer the ringing phone and both phones can talk with each other. As there are only two ports, the DLE-200B does not support dialing (for example, via extension number) and any digits dialed will be ignored. To configure things like how long the phone should ring or the duration for each ringback tone, read the manual and set the correct DIP switch positions. There are a few more switches on the motherboard (which requires opening the case to gain access), however none of the switches configures anything critical, and I did not change any of them during my tests.

After confirming that voice calls worked fine on my unit, I began testing data transmission. Using TeraTerm Web 3.1 connected to the internal modem on a Dell Pentium M laptop running Windows XP, I used AT command to call another TeraTerm session running on a Windows XP machine hosted on VirtualBox with a USB Modem connected to the host mapped as peripheral. The modems on both machines were connected to the DLE-200B. The Windows XP VirtualBox machine gets its Internet connection through an emulated Ethernet card bridged to my laptop’s wireless connection. Dialing from the Dell laptop was made using ATDT – any number is fine as the Viking does not support dialing and will just ring the phone once the line is off-hook. As soon as I saw “RING” on TeraTerm on the Windows XP VirtualBox instance, I typed ATA to answer the call. The two machines were then connected at 33600bps and data exchange could be made. Below is the screenshot of a ZMODEM data transfer in progress between my test machines:

Take note that the above steps are simplified and will work if the modems are data/fax modems and default to data mode. If the modem is a voice modem, additional AT commands may need to be sent to set the modem to data mode; otherwise the dial-up handshake will not be performed (you won’t hear the traditional dial-up sound) and data transfer will fail.

The next step is to configure my Windows XP VirtualBox instance to act as a dial-up server for Internet access, so that my Dell laptop can dial up to it. I had expected this to be a complicated process; however, as it turned out, I was able to do achieve the objectives with just a few clicks. First, open Control Panel > Network Connections and click on Create a new connection in the Network Tasks pane on the left:

Next, select the USB modem as the device to monitor for incoming dial-up connections:

In the next few steps, do not allow VPN connections (which is useless and will cause routing issues potentially blocking Internet access), select the users who can logon via dial-up and the protocols to be used (TCP/IP is recommended at minimum, or just select all including NetBEUI and File/Printer Sharing). Once done, an entry called Incoming Connection will appear under Network Connection – you can open this entry if you wish to modify any connection settings:

On the Dell laptop with integrated modem, I created a dial-up connection as normal. The number can be anything (123456 in this case) while the username/password should belong to one of the Windows users set to allow to logon earlier:

Clicking Dial to start the connection. Take note that Windows XP dial-up server might take up to 15 seconds to answer the call. For some unknown reasons (phone line quality or Windows XP bug), the first connection attempt will always fail with error “The remote computer terminated the control protocol” as shown in this screenshot:

However, subsequent connection attempts will work just fine:

The dial-up session is now established with the server and you can connect to the Internet at a speed of just 33.6kbps! As the version of Internet Explorer that comes with Windows XP is too old and cannot open modern HTTPS sites, I resorted to Mypal, which runs on Windows XP, supports TLS 1.2 and is still maintained. As expected, a 33.6kbps connection is too slow in this day and age, however text-only websites such as textfiles.com, lite.cnn.com or simple Google search works fine. Disabling Javascript and images will also help to improve the connection speed. The screenshot below shows Mypal browser downloading a PDF file from textfiles.com at 3.8KB/s, around the maximum expected speed for a 33.6Kbps connection:

On the Windows XP dial-up server, you can also view the incoming connection statistics:

As expected, the DLE-200B cannot do 57.6Kbps. Back in the heydays of dial-up, I was never able to download anywhere near the maximum theoretical speed on a 56K modem, which required special infrastructure support not available from my ISP. Even the DLE-200B user manual stated that the maximum dial-up speed supported is 28.8Kbps – I believe I was lucky to even achieve 33.6Kbps on my unit. In case you are wondering, dial-up connections are not feasible on digital VoIP gateways like the Linksys PAP2T ATA, primarily due to latency issues. I’ve tried it myself and the best I could achieve was a spotty 9600bps connection, not enough for anything except for transferring small text files.

With the Window XP dial-up server configured, you should also be able to connect from Windows 95 or Windows 98. Remember to select the dial-up server type as Windows 95/98/NT/2000 and not SLIP (Unix). As Mypal cannot run on Windows 98, you might want to try RetroZilla instead, which still supports Windows 9x.

Watch this video for the full 33.6Kbps dial-up experience using the DLE-200B telephone line simulator:

Download the DLE-200B user manual here. TeraTerm Web 3.1 (which runs on Windows XP) can also be downloaded here.