MCMF – MF4 dialling for the Psion MC400

Back in the early 1990s I was a serious Psion-a-holic. If there was such a thing as “Psionaholics Anonymous” I would’ve been there. My first machine was the ground-breaking Series 3 and I was instantly hooked. After that I owned a Series 3a, Siena, Series 5 and later a Revo. These machines had soul.

Psion Series 3a with Nokia 2140 (and Peugeot 205 GTi 1.9 keys) – a 1990s tech-feast!

I was a little too young for the original Psion Organiser (remember the YUPPIEs 😀 ?) that had introduced the Organiser Programming Language (OPL) – a structured BASIC-like interpreted language that meant owners could add their own programs to extend the functionality of these little handheld machines. The Series3 (and later) models had continued to feature OPL and added graphical capabilities to the language too.

I had missed out on the stereotypical 1980s-computerkid experience (ZX80/Spectrum/BBC Model B etc.) due to having parents that thought such things were a “waste of money” so my little Psion Series 3 was the first programmable real computer I owned (if you don’t count my programmable calculators that is… TI-66 & FX-4000P looking at you 😉 ). Over the years I wrote a large number programmes & apps for the Series 3/3a/5, and contributed to other programmers work too. (Including helping to test early versions of the controversial RevTran by Mike Rudin 😀 )

What a beauty… near-perfect keyboard and AA-battery powered.

I had always lusted after a Psion MC400 – a laptop size portable computer that ran for 60+ hours on a set of 8 AA batteries. The MC range was way ahead of it’s time, featuring a touchpad and beating any windows-compatible laptop machine at the time for longevity-per-charge but obviously restricted in features due to availability of software for the SIBO/EPOC16 operating system, proprietary SSD modules and a hefty price tag. I fell in love with it a first sight, it was an amazing machine.


From “Psion News” Issue 13 Summer 1992 – announcing the availability of Word Processing on the MC400

I finally got hold of a second hand one around 1995, just to satisfy my curiosity. I found one for sale in “Exchange & Mart” and had to drive a few hours from my home in Merseyside over to Lincolnshire to collect it. As the MC’s design dated from well before the EPOC32 days it had already been left behind by later Psion models. One of the many system functions that was lacking (but was a standard feature from Series 3 onwards) was the ability to play (DTMF) MF4 tones from the machine’s built-in speaker to enable the user to dial phone numbers by holding the microphone of a landline or payphone handset close to it. Phreaky!

As I was working in System Engineering for a major UK Telecom equipment vendor at the time I had easy access to the specifications of the MF4 signalling protocol.

I created an OPL program to generate MF4 tones which neatly integrated with the MC-400 system by allowing “bring” (basically single button copy/paste) functionality to get phone numbers from the contacts (or any other) app into the dialler.

Hi-tech holidaying…. accessing the internet via Psion Series 5 and (roaming) Nokia GSM phone. Torch coz no backlight on the Series 5 🙂

There was a thriving community of Psion users/programmers/enthusiasts on CiX (Compulink Information eXchage – a sort-of UK version Compuserve) where Psion employees would hang out too, and it was advice from here that enabled me to include system functionality into my OPL code. Colly Myers and David Wood – two of the key technical figures in Psion – had provided example code that enabled me to implement the missing “bring” functionality into Psion MC OPL.

And so in 1995 I proudly released my code to the world in MCMF10.ZIP … and then forgot about it. I think it may have been included in 3Lib (Steve Litchfield‘s freeware/shareware pre-Internet distribution service via floppy/CD) but I’m not even sure if more than a few people ever downloaded/looked at/used it. I did receive a couple of emails in 1997 from users referring to MCMF but they were asking me other general questions about availability of software for the MC platform. At the time of writing it’s still online in what looks like a CD collection from 1997. The MC was something of a commercial failure and never sold in any significant numbers (rumours were “less than 1000”), and I released my code well after the machine was on its way to being forgotten.


If you really wanna do some DTMF MF4 dialling on your MC-400 then download away…..

Text-based DTMF digit dialling heaven 🙂

I really really wish I hadn’t sold my MC400 – I would love to have it set up right now, even just as a terminal to talk to other computers with 🙂 I’m glad to see other people are actively keeping old Psions alive, even blogging/tweeting from an MC400!
UPDATE 28-04-2021: I managed to track down a working MC400 on eBay…. it’s just arrived today! Getting re-acquainted wth it….

Psion MC featured in an advert for Psion Dacom “compact” modems 🙂
From “Psion News” Issue 13 Summer 1992

Just in case you were wondering – all this nostalgia was started by the acronym “MCMF” popping up at work, but in this case it was “Multi Constellation Multi Frequency” referring to GNSS receivers 😀

From “Psion User” Summer 1996 – the nascent www and Psion’s own website

Published by zedstarr

Chilled out human being, doing techy stuff.

One thought on “MCMF – MF4 dialling for the Psion MC400

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