I am really very pleased to see someone interested about the particular dead branch of computing history known as the Tandata PA. I spent many years working on it, among others, and I don’t think its importance as a historical artefact is appreciated. The fact that it was designed and built by a company that was only known for Viewdata-type terminals means it is often confused with being just another terminal. The thing to understand about the PA is that it was a portable computer – what we would now call a laptop. Admittedly, a portable computer optimised for communication with host systems cleverer and more capable than it. For context, Wikipedia says that the first recognisable laptop – battery powered, LCD display, for use on the move (as opposed to the “luggables” that could be carried from office to office and had to be plugged to a socket for use) was the Epson HX-20, announced in ’81 and widely sold in ’83. Development started on the Tandata PA in the second half of ’82 but only really kicked off in early ’83. The product was finally launched in the back end (October?) of ’85 and sold from early ‘86. The first and only UK entry in the Wikipedia history of laptops article is the Clive Sinclair designed Cambridge Z88, first sold in 1988! The Z88 is also credited with being one of the first PDA’s – ha! The clue’s in the name – Tandata P.A. So, the Epson HX-20 had a 20 character by 4 line LCD display. The Tandata PA launched two years later had only 20 characters by 2 lines, but it was a very different beast at a time when it really wasn’t clear what a portable computer should be. The Tandata PA was all about comms. Comms and Email in the early 80’s was very different from today – no internet! BT operated the Viewdata service, which was mostly about looking up things – it was connected to Travel agents, so you could browse and book holidays, it was connected to the Bank of Scotland, so if you had a special account you could see your account and even could pay bills! It also had a rudimentary email system where you typed into a fixed-size small box on a screen, and sent a message to another Viewdata user whose email address you remembered. The service was mostly aimed at consumers. There was a second system in the UK, BT Gold from BT. This was no more and no less than a login to a timeshare computer. You dialled up and were presented with a simple flashing prompt. If you typed “mail” you entered the email programme. You typed live into the screen, and pressed control-Z at the end to send. But only, of course, to other BT Gold subscribers on the same system. Because BT Gold email was not limited to a single screen of text, it appealed more to commercial users. We judged the small LCD display on the PA was sufficient for portable input and editing of messages - offline and battery powered. No “mobile data” obviously, but with the PA you could create a message while on the train during your morning commute, and when you got to your office you plugged it into the phone socket and sent it. Revolutionary! In addition to the word processor you also had a calculator with paper roll history, a phone book, a diary with settable day and time reminders and even a spreadsheet – everything a busy executive could need to set up his day in the office. When he (always a he!) gets to the office, plug it in and you had a modem to dial, a 40x24 colour screen for Viewdata data lookup, a 80x25 mono display screen for BT Gold, RS232 to connect directly to the company mainframe with Dec VT-100 and IBM 3270 compatibility, a printer port (inside your office it would be completely paper driven), and the least-understood part of the design, a second, pass-through phone socket. Plug your standard desk phone into this socket, and the PA would monitor the activity, noticing if you picked up the phone and offer to dial for you, or dial from the phone book, etc. The original design even included a loudspeaker and microphone to act as a loudspeaking phone, however the approvals process needed to get a fully functional active phone approved for connection to the BT network was too onerous, and the microphone had to be dropped. With this understanding you can see the reasoning around the decision the device was most criticised for – no removable storage media. You do not need to keep data on the device long term – you upload it (or “send Email” as we would now say). Finally, (ta-da!) the PA was not only multi-tasking and multi-user, but even “timesharing”, potentially enabling a Manager and a secretary logging into the same PA at the same time to edit different documents! Try doing that even with modern laptops without a server. Nowadays the device would have been subject to a whole bunch of patents but in those simpler times software patents were simply not considered. So what went wrong? Two things. Mostly, the market was not ready. The need for a portable device was not developed – our Unique Selling Point of a portable device was a curiosity not a must-have. I remember we launched with a full-colour A4 glossy of a man (told you) sat on a train, typing. I would love to see a copy of that preserved on the net somewhere, but it is almost certainly lost. However the initial reviews instead focussed on the PA as an up-market “executive” viewdata terminal. In the absence of market excitement, Tandata soon retreated to its core market of Viewdata users. In the Wikipedia article it is notable how many of the early devices were failures to some extent or other. The market for battery powered mobile devices was not ready. The second thing that went wrong was a famous random failure mode discovered just after launch that took too long to fix, an unfortunate combination of being too ambitious and plain bad luck. The PA was designed never to be really switched off. Almost (totally?) unheard-of at the time, there was no power switch, just a signal switch that basically said the user wanted the system to enter a low-power mode (now familiar on laptops as stand-by mode). This was needed because the PA had a real-time clock and was supposed to wake up for diary alarms and even auto-answer the phone. That was the ambition. The bad luck, was that the physical design required the PCB to be mounted upside down in the case. Not a problem usually, but the software was burnt into eproms and so sockets were used to enable the software to be upgraded. If the PA was dropped hard onto a desk, the eproms might loosen in their sockets for an instant and if the PA happened to be on at the time it would briefly execute random electrical noise. A disastrous event for a machine designed to be moved with no backup media and no hard reboot button. With such complicated software obviously we thought it was a software bug not a hardware fault. It took us months analysing return-to-factory units – all we could ever see was that for some mysterious reason the CPU had taken a machine-gun to the filing system. Solved eventually of course but the damage was done. The first production run was 1000 units (not bad income at almost £1000 a pop), and I think there was a second run, but that was it. However I do know every single PA was sold, which is why there are so few left now. The big companies who bought the PA’s in bulk would have disposed of them responsibly after many years of dedicated use. There was never even a small pile of unsold units for the enthusiastic amateur to salt away. Sorry about the above screed of text, but as you can see I think that the innovations of the device have never been recognised. I always wanted to amend Wikipedia to include this UK first, however Wikipedia is not the place for original work - it needs to reference definitive articles elsewhere on the web, and no such web page has ever existed for the PA. Perhaps if you publish such an article, you and I can right this historical record injustice… On to your device: It seems an early model with upgraded software. The EPROM marking is fascinating – DENIS means nothing to me anymore but we were very fond of puns and jokes so it probably meant something funny. The important part is the V1.3b designation. There was never a V2, but I remember letters up to at least g, and at least .4 and possibly .5, so V1.3b indicates it’s mid-not-late software. The daughterboard V39 marking is even more revealing to me. I was only one of a team contributing to the main V1.xx software, but the daughterboard was all mine! I remember issuing at least a V40 and V41. As befits an I/O module, the software version numbers usually tracked hardware changes and was largely unconnected to the main board software, so V39 indicates an early machine. Finally the question mark that replaces the full stop on some EPROMS is most revealing of all – we must have been patching some of the software on some of the EPROMS without a full clean rebuild which was last done on 29/7/88 apparently, hence the questionable status of the version of some of the EPROMS. This patched software would be development only and never reach retail units. In summary your machine is not straight off a production line and it was loved and cared for by myself and others in our Cambridge development lab.