Sharp EL-808 Calculator.
Date introduced: 1974.
Date discontinued: 1975.
Main IC: NEC UPD224C.
Display: DSM LCD.
Functions: Addition, subtraction, multiplication & division.
Digits: 8, fully floating decimal point.
Power: 6V, 4xAA batteries or external power supply.
Original purchase price: JPY24,800 - Adjusted for inflation to 2020, somewhere around GBP2,000.
(Larger versions of all images on this page can be accessed by clicking on them.)
The late 1960s and early 1970s was a period of fierce competition in the calculator world, with each manufacturer bringing out machines with new features, that were smaller or cheaper than the competitors seemingly every other week. In terms of features this example from 1974 is utterly unexceptional...A large handheld or compact desktop calculator with the standard four functions really wasn't anything to write home about. What set this aside from most calculators at the time however was that display. The EL-808 was in fact only the second model to ever be sold featuring a liquid crystal display, the first being the EL-805 released in 1973 also by Sharp. Unsurprisingly Sharp were quite proud of this so it's prominently shown on the display hood.
This however isn't an LCD as you most likely know it. A typical LCD looks something like the one below, modelled for us by another Sharp calculator, in this case an EL-8130A from 1977.
This "normal" LCD is a Twisted Nematic display, and works by either allowing or blocking the passage of lights by changing the way it is polarised. These became commonplace towards the mid-late 1970s and are still commonplace today. Some of the earliest ones had a yellow filter over them, but the technology was pretty much identical. The yellow filter was mainly due to the fact that there were some concerns about how stable the early displays were when exposed to UV radiation, so the filter was fitted to ensure that the displays wouldn't degrade over time. It also helps to improve visual contrast a little.
The display on this calculator however is a completely different beast. This is a Dynamic Scattering Mode, or DSM LCD. These operate in a completely different method to Twisted Nematic displays - about the only things that they actually share are conductors being deposited on glass and that the active element is a liquid crystal compound.
If you've never heard of a DSM LCD before don't be too surprised. They really weren't around for long at all, being almost entirely ousted by Twisted Nematic displays within a couple of years. Calculators using these displays were quite expensive as well so they were never massively common.
I'd noticed in photos of some early LCD calculators that they showed white digits against a black field but I never really gave it much thought...As you may well know, if you flip the front polariser on a modern LCD you will reverse which portions show as transparent or black, so you'll end up with white digits on a black field. I had always assumed that these early calculators just had that sort of arrangement and pre-dated black digits against a grey field being chosen as the standard...I'd never even considered that the displays were hugely different in how they worked.
There are no polarisers involved on a DSM display. In the rest state the liquid crystal compound in the segments of a DSM display sit in an ordered manner, meaning that the segment appears completely clear. When power is applied (if my understanding is correct, around 15V AC) to the segments however the crystal structure is disturbed. The resulting visual effect of this is similar to frost appearing on a sheet of glass.
The way Sharp used this to create a good visual contrast was to place a mirror immediately behind the display. This isn't immediately obvious if you're just looking at the display from a normal viewing distance and angle, it just looks like a very clear light on black display.
At extreme angles it's obvious that this isn't a conventional LCD as it doesn't "wash out" like a normal one would.
The reason it appears that the digits are on a dark field despite the backing actually being a mirror is because if a bit of quite ingenious design on Sharp's part. You may have noted the hood over the display here (which to me makes this calculator look extremely like a Tricorder from the original series of Star Trek), the underside of this is lined with a black short pile felt.
...Said felt also does a passable impression of Velcro and as you can see has no small amount of fluff stuck to it! I haven't figured out a decent way to clean it properly without removing the hood, which isn't a trivial operation. So what you actually see in the mirror is a reflection of this black felt. A little illumination is provided to the display from the side through a little window along the top edge of the case.
Because of the sort of "satin" texture of the digits this makes the display very clear, even in relatively poor light.
If you place something white in front of the black felt of the hood however it clearly shows that there is a mirror behind the digits.
Looking closer and at a lower angle you can see the mirror and almost frost-like appearance of the digits. Oh...and lots of bits of shed fluff from the felt on the hood. Sorry...I should have cleaned the display before I took this photo.
What is much harder to capture on camera though is the "texture" of the active digit segments...They're almost retro reflective. What is impossible to capture on camera too is that the reflective pattern on them is not static either...If you look close enough you can actually see the digits "shimmering," especially while they're in the process of switching states. This really isn't something you can show in photographs...you need video and a *really* good macro lens. Helpfully, a gent has both of these things covered on this YouTube video. The camera work there is absolutely gorgeous.
I wound up taking a load of photographs of this display as it really is a thing of engineering beauty...it would be a shame not to share them, especially as there aren't nearly as many detailed photos of DSM displays out there as there deserve to be...so here are a few.
The actual character structure is the "normal" LCD style, nothing really unusual there. The negative sign indicator is to the right of the main display, it always appears there, rather than using the centre segment of blank digits as some calculators do.
The flash does show the texture of the digits a bit better.
I must have lost a good hour or so just looking at this thing.
I really need to try edge lighting this with some coloured lights and see what I can do. I'd love to try to get some video, but I just don't have a camera with sufficient macro capabilities to really do it justice.
While DSM displays are downright beautiful to look at, Twisted Nematic displays are from all technical aspects vastly superior...They use an order of magnitude less power, are far easier and cheaper to build, can be made far more compact, have massively faster response times and are more reliable...As such it's hardly surprising that once they'd got the manufacturing methods sorted out that DSM displays disappeared almost overnight. Really the only aspect where a DSM display wins over TN is that the viewing angle is essentially unlimited...but that's really not useful in enough circumstances to ever have given them a hope of remaining in production once TN LCDs had got a foothold in the market.
This was an expensive calculator for its day for a desktop four function unit. However it's absolutely obvious that this was a model designed to showcase the then cutting edge display at its best, and the whole thing is a very attractive unit. I didn't remember seeing it in the original sale listing, but this one came in its original leatherette slip case.
The moment you take it out of the case the immediate impression is one of a quality instrument.
The leather effect texture covers the front surface and the side cheeks, and even the centre of the power button.
The lines bordering the model tag and power switch strip are the only actual bright work, the rest is satin aluminium, but that little bit of bright work is just the right amount I think, it looks classy. Any more and it would risk looking over the top.
The underside of the case doesn't get quite such attention to cosmetic details - but it's notable that there are no moulding marks or anything left on show.
I assume they've hidden the injection moulding mark for the case underneath the rating/serial number label.
Note the power rating...0.4W. For an LCD calculator...Therein lays the biggest drawback that DSM technology had compared to TN. Between the step up circuitry needed to boost a battery supply to the 15V or so needed and the actual consumption of the display itself, it could never hope to compete in that regard. For comparison...The Sharp EL-8130A calculator from 1977 I borrowed for a comparative display photo at the start of this page has a rated power consumption of 0.00035W. The EL-808 here draws 1,1423 times as much power as the EL-8130A which uses a conventional TN display.
The battery compartment helpfully has one of those ribbons to help remove the used cells, which are normal AAs in this case. Unusually they're all fitted facing the same direction.
There's only one screw holding the case together, hidden under the batteries, then the case clamshell pulls apart from the top. Took me a while to figure that out as the case is exceptionally solid, there really is absolutely no give in it anywhere. Plenty of length on the power lines to allow the case to be opened up without needing to disconnect anything.
Shows that by the early 70s there really wasn't much in a calculator any more! The size of the display assembly and the battery compartment pretty much defined the size of the case. The little PCB to the left of the battery compartment appears to be a capacitor to help smooth the input voltage. It's worth mentioning that while I haven't seen an actual manual for this machine I've seen a few websites noting that the 6V input jack on this may be centre negative, so if you want to power one of these from an external supply it would be well worth double-checking that. Feel a bit silly for not checking that while I had the case open now...Looking at the wiring there it does look to be the case.
There's not much to this PCB really...One main "calculator on a chip" in the form of an NEC UPD224C, a couple of passives and I believe most of the other circuitry is to drive the display.
I would have liked to get the main PCB out to get some closer photos of the display, but sadly one of the screws behind the keypad has a rounded head (it was like that when I got to it, I'm not guilty!) so I couldn't get the PCB out. I may revisit this one day as I really want to get some proper close ups of the display without the case hood in the way.
The other thing of note in here is the nicely designed switch they used to actually turn the calculator on and off - this is done automatically when the hood over the display is opened, it pops up when you press the power button.
Nicely little designed reed switch there.
The case went back together nicely without any drama whatsoever. Astonishing how solid thing thing feels given there's only one screw and a couple of clips holding it together.
It's a bit big to call it handheld, but it does feel good in the hand.
The heft it has to it probably helps there...Not a lightweight you're going to want to carry around in a pocket.
That's 460g, or a shade over 1lb for those of you not using metric.
Size-wise the footprint is pretty similar to most compact desktop calculators. Here it is next to my Kovac K-80D.
The feeling of quality extends to the keypad, it's not quite "clicky" but does have a really nice short throw tactile action to it, and has a dimple in the 5 key to help with the ability to enter data without needing to watch the keypad. The key legends are overmoulded too, so there's no silk screening to wear off.
It is very basic keypad though given it's just a four function calculator without even any memory capabilities.
In terms of operation there don't seem to be any particularly glaring glitches I'm aware of. The only real quirk I've noted is that when in division mode it does not suppress trailing zeros, so if you input 2/2=rather than showing 1, it will display 1.0000000. Not really a problem, but just something to be aware of.
Overflow or arithmetic errors are indicated by the display showing all zeros with all the decimal point indicators lit.
Underflow is shown identically but with the negative indicator shown.
It's such a nice looking calculator that this one will probably remain a permanent resident on the desk. DSM displays were such a brief thing that it's really nice to have one in the collection.
If anyone's got any particular comments of questions on this one please feel free to let me know.
I don't have a copy of the user's manual that would have come with it or the original box sadly. So if you've got a good photo of the box or a good scan of the manual that you'd allow me to add here I'd be really grateful if you could get in touch.
29th December 2020 at 20:01 - Page created and uploaded.
26th January 2021: Minor page formatting changes to improve readability on mobile devices.