The MMUX is no longer in production. This page remains mainly for existing customer product support and reference.

The product simply reached the end of its life for ISP use. "Modem pools" are not made out of physical modems these days, in fact "modem" is rapidly becoming a word of the past.

The MMUX was very attractive to system builders and people prepared to hack, and I expect there would be quite a few units out in the world, still running in ISPs happy with 33k6 modems, Quake servers, fax on demand, voice mail, telemetry systems, or some other obscure role. The MMUX was not however a good turnkey solution - have you ever installed a COM port based anything and not run into problems?! You can imagine the support required as a diverse array of global customers tried to fit the MMUX into their diverse arrays of equipment. Our closest competion was four times the price for a reason.

Still, it did work, and work very well. We can still manufacture if there is demand for a significant quantity (like 8 or more) as parts remain in stock. The remainder of this page has been left largely as it was in 1997 (old email addresses removed, site navigation updated).
(C) Copyright 2001 ADX Electronics.


The Modem Multiplexer was designed for PC based Linux systems, and allows the use of up to 128 internal modems on a single machine. It is an inexpensive way to provide internet services. This makes especially good sense if you want to hold off committing to the expense of one of those experimental new standards. It is also a handy way to access the features of multiple voice/fax modems, or other UART based products such as serial cards or ISDN adapters.

picture of MMUX controller card

We supply the small 8-bit controller card (above) which plugs into the host PC, a special motherboard (below) which your modems plug into, internal cable, the interconnecting cable, manual, and drivers. You supply a standard PC case with power supply and 2* DB25 cutouts (since all 8 slots are available for modems).

picture of the backplane board

SPECIAL INTRODUCTORY PRICE: The basic 8 modem system above is US$295. Additional backplanes (up to 4 per controller card) cost US$200 each, and additional controller cards (up to 4 per host PC) are US$95. Quantity discounts are available, and we can maintain the introductory price for early buyers! If you save $20 on each modem by going internal, then our parts almost 'pay for themselves'!

System stability will be high on your mind - the first Modem Multiplexers have been working fine at the ISP for more than a year. They say that using internal modems has generally been more reliable than their external modems - and having all the modems neatly mounted in cases is a definite advantage. Modems can be individually and remotely hardware-reset if they misbehave.

Product support is probably also on your mind. Don't hesitate to email or fax us with your suggestions/questions/abuse, "our engineers will be on it" immediately. We are small enough to respond to your needs, but big enough to know what we're doing.

The Modem Multiplexer is designed to work with any standard internal PC modems or serial cards (including ISDN). The original 'personality' of each modem remains, with a remapped serial port. The Modem Multiplexer takes advantage of the 16550 UARTs on all fast modems. This results in throughput usually only available with intelligent multiport cards (contact us for figures) but allows the use of standard, proven serial.c code.

Software info: There are three linux kernel patches available which contain the source for the modem server; one for kernel version 1.0.9, one for 1.2.13, and one for 2.0 kernels. Much of the serial.c is unaltered, as the modems emulate a standard serial port. Complete installation instructions are included, and updates are available on the net (site no longer exists). Drivers for other systems are in the pipeline.

We accept payment by Visa or Mastercard. Shipping weight for basic system is less than 1kg.

The Modem Multiplexer was developed by Mark Tomlinson for the ISP he co-owns and runs: (now closed down). Antony Dean 'is' ADX Electronics - contract design, car audio, micro and power electronics... We are both electronics/software engineers by profession. I have helped Mark with the production engineering and manufacturing of the Modem Multiplexer. New to the Modem Multiplexer team is Chris Edsall, experienced in Linux and web page design.

(Specifications may be subject to change - contact us for specific enquiries. All pages (C) ADX Electronics 1997)