Sinclair ZX81

The world around the Sinclair ZX81

The Sinclair ZX81 deserves more credit than what's usually given. While many could afford Tandy’s, Apples, and other computers of the time, the rest of us, mortals, simply could not even dream of a computer at home. Such luxury would have been impossible.
And then Sinclair comes to the rescue with the ZX81; and for about $100.00 ($149.95 assembled) you could be part of the computer revolution. And that, my friends, made you feel pretty special. The ZX81 was my first computer. I remember when we hooked it up to the TV, and turn it on. I felt like I was in at NASA Mission Control.
And then just like a science fiction movie, you were immersed in this magical world, and you started looking for all those cool peripherals!

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ZX81 Ad

The ZX81 was unbeatable for the price. It made home computing affordable, allowed a lot of people to experiment with their first computer, at home.(Sinclair User)

ZX81 Ad

It's American cousin, the Timex Sinclair 1000. The ZX81 was licensed in many different countries and sold under different names (Sinclair Catalog)

ZX81 Ad

Its predecessor, the ZX80. Equipped with a "chimney". It had a friendlier look, and looked more like a consumer electronic device that the ZX81 (Sinclair User)

ZX81 Ad

You could choose to buy it as a kit, and save some money. (Sinclair User)

1. Sinclair ZX81 external keyboards

I am one of those few who actually think the ZX81 looks great. And I would even throw out there this may be the most future looking, space era, sci-fi device you could have at home, at least back then. Sure, it was a monochromatic Speak & Spell (TI's toy computer - You can look it up), but it make you feel like Captain Kirk on the Enterprise.
Anyways, It look great, but the keyboard was borderline impossible to use. 
Honestly, to do anything seriously you would have to do something about the keyboard, or take Xanax, do yoga, breathing and meditation, all at the same time.
So another chapter in the history of "Frankenstein" computers was open.  You could actually get a keyboard from a number of small manufacturers. The installation wasn't easy though. You actually needed to open the ZX81 and connect your keyboard to the internal port where the actual Sinclair keyword was connected.
But hey you ended up with a real keyboard. Real? Well, look at the photo. And, by the way, you did not type as in a regular computer. Remember, the keys were mapped to functions, as you can see in the Sinclair standard keyboard. Anyways it did work. It also felt a little bit more adult (no Speak & Spell); you could even pretend this was a real computer.

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ZX81 Keyboard
To add more cards, hover on a card and click 'Add items'
Basic Keyboard attachment

A simple, inexpensive and convenient solution. This just sits on top of your ZX81 (Sinclair User) 

Very basic keyboard

You asked how bad it ZX81 keyboard. Bad enough that you would spend money on this (ZX Computing)


This look better than the other options, but it was still so primitive (Sinclair User)


An early form of plastic surgery. I would not give up the looks of the ZX81. I would just want to add the keyboard externally (Sinclair User)

Sinclair ZX81 16K RAM Expansion

As much as I like to glorify the Sinclair ZX81, I have to be honest there wasn't a lot you could do with it. First things first, you needed more memory; let's be honest 2K RAM was not going to get you very far.
The most popular device for the ZX81 was actually the 16K memory expansion which connected to the rear expansion/connectivity port on the back.
Cosmetically, I think it look great, very Sci-Fci, like a device out of star Trek. You would gently insert it (this thing was fragile) and just like enabling the transponder in a nuclear submarine: 16K. Functionally, it was not great. The port was not very sturdy, and movements of the computer could cause a bad connection and you end up with your first frozen screen / crash.
So the memory allowed you to either load longer programs from cassette, or write longer programs (if you were actually typing on that keyboard). While the 16K module was sold separately, it was quite essential to use the computer and run any software. There was virtually no program for the ZX81 that could run on 2K. The question is: why just not put 16K, or sell the thing as a package.  

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16K Memory

It would be difficult to find a photo of the ZX81 without its memory expansion module. Although it was sold separately it was quite essential (Sinclair User)

Sinclair Software

This ad, showing software available, shows a ZX81 with its memory module. Once again, essential (ZX Computing)

Sinclair Software

Aside from the Sinclair version, you had other manufacturers, who promised a better fit (ZX Computing)

Cassette tape decks, audio cables, and storage

Sinclair really wanted to make things easy for us. And by easy I also mean affordable. To effectively operate as Sinclair ZX81 you did not need a ton of accessories (when I say operate, I mean do the few things you could; no hacking NASA or the CIA on this little thing).

So in terms of storage, you only needed that cassette tape deck. This you probably already had at home (like the one in the photo). So basically you just needed to buy an inexpensive microplug audio cable, and that is it. Now you had your "digital-analog magnetic sequential read/write storage device". Slow and somewhat unreliable, but hey, you got a computer in which you could load games and save your fancy computer programs! Now you can go and buy all that awesome software that came in cassettes. Word of advise, make a bunch of copies, just in case. 

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Panasonic tape recorder
Growing your computer Website Builder

Someone was a little bit ahead of its time here. Is this a 16K solid state hard disk? (ZX Computing)

Tape Controller

Not even sure if this is good, bad, or what? It is definitely necessary. I guess with this you are half-way between a cassette tape deck and a disk drive (Sinclair User)

Tape Controller

Sounds reasonable! (Sinclair User)

Tape Controller

Plenty of options if you did not have a tape deck at home (Your Sinclair)

ZX81 Sound Synthesizers

The ZX81 had neither color nor sound. The idea of any of these things was simply unthinkable. For those who had a ZX81, this is what we would talk about in our dreams, a computer with color and sound. In fact, from a technical perspective, it was pretty much impossible to add any of these.
But then these comes up, and voila, you have audio. Basically there were two flavors: one is really a little bit of a scam. Basically what they did here was prerecord sounds, on ROM, and by calling the right memory addresses, or just writing the right command, the thing would play the sounds. It was a clever trick to keep up entertained while waiting for the Spectrum. Of course, this was quite limited, the sounds were explosions, lasers, shooting sounds, etc. I give this some credit for coming up with a clever solution to pretend you had a computer with sound.
The other device, was more like a synthesizer, where you could control frequency, attack, delay, etc. And this had some potential. 

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Sound Cards / Interfaces

Naturally, if you can generate sound, you can "talk". More below (ZX Computing)

Indeed, every computer need this... (Sinclair User)

Sound with your Sinclair

And as copycats rise, prices dropped quickly (Sinclair User)

Music Sythesizer

Why not throw in an I/O line to send active 5V pulse to TTL devices. From the picture you could create your own terminator (Sinclair User)

Voice Synthesizer

If you just finished reading the section on sound synthesizers, you may be wondering: what about voice? To be completely honest, the manufacturer could have had some prerecorded voice “sounds” in the sound synthesizer mentioned above. But i guess it is more lucrative to make two separate devices and cash it, while it lasts.
The principle here is the same, although the device is a little bit more sophisticated, because when you feed it a word, it will have to play the different sounds that make up that word; but that is just software. Technically, it is the same hardware, or very similar. And while hardware was the same, the wow factor of a talking computer was a lot higher back then. Trust me, around that time, if you bought a ZX81, you were not expecting it to talk. Sadly, in the end, it was just a useless gadget that would probably end up in a drawer a few days after you got it.

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Voice Synthesizer

Of course, once someone figure out how to make the ZX81 talk, there were copycats everywhere (Your Sinclair)


How fantastic Spectrum voice generation was? If you ever heard you Spectrum talk, you know it sounded terrible (ZX Computing)

Sound and Speech

This was really something that took off, and generated a lot of sales (Sinclair User)

ZX Printer

Back in the 80s, standing in front of a computer retail window was magical. The Commodores, Sinclairs, Radio Shacks, all their accessories, television with some dumbed-down version of an arcade game. Everything looks awesome, high tech, and very desirable.
The one thing that did not cause any fascination from my part was the ZX printer. Even back then I could tell it was useless. Even more useless if you connect it to a ZX80/81. What could you possibly want to print in a 4 inch wide paper (rolled). Was Sinclair hoping that someone would use their computers to print supermarket receipts?
I have no idea how may they sold. They could have probably saved money and time by not making this.

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ZX Printer

The ZX81 had limited printing capabilities (ZX Computing)

While printers were not the most popular accessory for the ZX81, there was still a markets, and many vendors (ZX Computing)

In the US, the 20-40 was sold by Sinclair and the official Timex Sinclair 1000 printer. For the UK market is was offered for both ZX81 and Spectrum (Your Sinclair)

32K and 64K Memory Expansion for the ZX81

I have two theories behind the existence of a 64K expansion for the ZX81. My first theory has to do with the lack of information available (at the time) on what it meant to add more memory to a computer. I would assume that some people would have bought this expansion device thinking that the computer would become more capable. And that, in a way is true, the computer had more memory; but more memory for what? There really wasn't any software that required 64K. Unless you were trying to write software that will require 64K, this did not make sense. People who intended to write software that required 64K on a ZX81 would probably be better off investing on a better computer. And really, writing any code on this machine was a pain. Needless to say, this 64K memory expansion would not bring color or sound to your ZX81, which is what everyone wanted. 
Theory number 2 has to do with marketing the device for purposes of status: I have 64K on my machine, and my car has 8 cylinders and 300HP. I know it sounds strange, but maybe in some small circles, this was a measure of power, success, and glory. I guess if you met with a C64 user, you could tell them you also had 64K computer.

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Expansion Units

So much software!

Like any other computer, much of the success of the ZX81 was due to the availability of software. While mostly games, there were also some educational and productivity applications available; in fact, there was a version of VisiCalc that was ported to the ZX81. A lot of credit needs to be given to whoever managed to put a spreadsheet software on a ZX81.
A fortunate, or unfortunate factor that contributed to the growth of the ZX81 (and other computers of the time) was that cassette tapes could be easily duplicated. This may have been the beginning of computer software piracy, but in a way, without it, the computer industry would have not had the market penetration it did. Cheap, or “free” software reduced the overall cost of owning a computer. Keep in mind that at that time, a computer was not seen as an “essential must-have” tool, but more as an accessory or entertainment gadget. Any price improvement would make it more accessible. Overall, cassette tapes played a critical role in making the ZX81 popular across the world. 

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Software and more Software

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