Zx81 projects. The main keyboard circuit is also almost identical to a ZX81s, with the addition of a Arduino Pro Micro enabling the ZX-Key to be used as a regular USB PC keyboard. This is all well and good, but why use an X11 windows manager when we don't really need to. As it turns out (thirty plus years on Feb 14, 2017 · At the end of the last article, 'Simple Start To Retrofitting A ZX81', a new power supply was sourced and a composite video mod was fitted. It uses Z80 CPU and Dual Clock boards from Baffa-2 Basic set and has 32KB RAM, 4K/8K ROM option (ZX80/ZX81) and allows you to use a PS/2 or original keyboard May 29, 2019 · The ZX-Keys mode indicator LEDs and reset switch are slightly recessed at the back, with some nice speed lines running either side, lending a retro 80s feel. 20 Simples Electonic Projects for the ZX81 & Spectrum. In reality it's the first project of the book, even if it's not fully described until Appendix A. Special thanks to Paleotronic for both suggesting and providing the space the Spectrum game and a shout out to Rod Bell for supporting the project. The ZX-Key Minstrel adapter is really just a simple breakout board for the standar ZX-Key keyboard. folkscanomy_computer_inbox; folkscanomy_computer; folkscanomy; additional_collections. Language. There was this ’81 networked with an ESP8266 , or this vintage Maplin I/O board completed Sep 26, 2018 · complete-timex-ts1000-sinclair-zx81-rom-disassembly Identifier-ark ark:/13960/t5v76pb7r Isbn 0861611136 9780861611133 0867591242 9780867591248 Ocr ABBYY FineReader 11. While resourceful owners could accomplish a lot with the 1K or 2K of RAM built in to their computers, more serious uses required more RAM. All three of these projects have now been merged into the newly released ZXvid module. It's based on Grant Searle's ZX80/81 Project, heavily inspired by Wilco2009's Board (Alejandro Valero) and my own experience after had built it ( and fixed some Zeddies). The battery is rather important as the static RAM is the internal storage medium, there are no flash drives in thid machine. Some fixes applied due to changes in the Arduino library since Apr 16, 2023 · All three of these chips are period correct for the ZX81, in production and available of the shelf today (at least in 2023). Provision has been made for mounting it firmly to the Minstrel, held in with a bold ZX-Key ZX81 Interface Guide Book. Jan 22, 2018 · I've been meaning to write something about the ZX81 Ethernet adapter Zeddynet for a while now, but hadn't got around to it for various reasons. English. Read about, play, run, or list games, animations, and more. The Interface Card holds all the logic an ICs, and is where all the 'magic' happens. Dec 3, 2020 · 20 Simple Electronics Projects For The ZX 81 And Other Computers : Stephen ADAMS : Free Download, Borrow, and Streaming : Internet Archive. Daykin for Maplin's 'Project Book 04' from 1983. 3v) Arduino boards. The final piece to the ZX81 keyboard puzzle is to get the Raspberry Pi / AZ15 to boot like it's 1981, arriving straight at the Sinclair "K" prompt after being switched on. 20 Simple Electronic Projects For ZX81 - 20 Simple Electronic Projects For The Zx81 By Stephen Adams. 64K RAM (Sinclair Place) - Gold-plated connectors and power LED. Stephen ADAMS. The need for extra commands to set extended emulation behavior have been removed. Sep 24, 2016 · The Recreated ZX Spectrums Mode 'A' Key Mapping. by: Jenny List. The New Tynemouth & TFW8b. Apr 1, 2018 · Re-Design the ZX81 Decoder Board In the previous blog entry I left off before starting design work on the Decoder Board. Jan 6, 2017 · This appears to be the first ZX80 we’ve featured here, but we’ve brought you ZX81 projects aplenty. Miscellaneous projects related to Sinclair computers. A JLO FDD Interface Hardware Project. 7. Aug 30, 2023 · ZX81 Tactile Keyboard Rev. The ZXCCB video mod, the ZXVid and others, are designed to take full advantage of the Composite inputs, outputting a stable and clear image to modern LCD TVs. May 2, 2013 · Download sz81 for free. These are my programs from the ’80s to today. With a Z80, 1k of RAM, a That's about it, be sure to check out the article in Paleotronic and enjoy both the original and especially this ZX81 enhancements. Topics. The when complete the MyTeSeD can be powered from a 6v to 9v battery supply (like most Arduino projects), in addition usage of the Nano conveniently provides a means to power the interface via the mini USB Jul 28, 2020 · Easy add-on projects for_Spectrum, ZX81, AceBERNARD BABANI (publishing) LTD Nov 3, 2023 · Description. pdf is the schematic of the corrected revision 1. The file ZX81+38rev1,5. May 20, 2018 · The light pen featured in Easy add-on Projects for Spectrum ZX81 & ACE does not work in the typical way. For this there are two options, either connect directly into the heart of the machine replacing the existing membrane keyboard, or build an external expansion interface card for ZX81 and keyboard. Provision on the base has been made for standard 12 x 12mm rubber feet to stop the keyboard from sliding around on a table. Nov 10, 2022 · Building A Sinclair ZX81 In 2022 With All New Parts. This of course is where the Minstrel Issue 3 comes into the picture, it being the first of Dave's fully functional ZX81 clones-ish computers. Note that if using period RAM expansions such as the 16k Sinclair RAM pack or one from Memotech, then hardware alterations are required. 5mm) between the two cover parts (as suggested in Nov 19, 2017 · The Sinclair ZX–Micro Computer: System Variables Comparison Chart. At the rear of the case the IDC connectors for serial out ZX81+38rev1,5. Dec 1, 2023 · A tag already exists with the provided branch name. Apr 8, 2024 · Behind the scenes, I've implemented enhancements to optimize how levels are stored, Refined game timing to synchronize directly with the clock cycles of the ZX81/Z80, resulting in smoother gameplay. [Retro Shack’s] ZX81 died, and while he tried to figure out the fix, he decided to build a new one. Sinclair and Timex offered 16K RAM units for the ZX80, ZX81 and TS 1000 computers. While the battery was still holding charge, it Mar 13, 2021 · As standard the ZX81 comes with 1 KB or RAM, which even in 1981 was very little. Preliminary Sketches are written to be used with an Arduino Leonardo and USB Host Shield, however they should work without major modification on Pro Micro (3. Mar 4, 2011 · Tomorrow, 5 March 2011, marks the 30th anniversary of the arrival of the machine that did more to awaken ordinary Britons to the possibilities offered by home computing: the Sinclair ZX81. The original Java ZX81 emulator! I wrote this during the 98/99 academic year for my final year university project 22 years ago :-) Now available again with source code, and patched to compile and run with the latest version of Java (SE 15). This blog entry I'll take a quick look into the ZX-Key Expansion interface required to get the ZX-Key Keyboard working with a ZX81. This is a copy of the sinclair ZX81 from 1981. Diodes can be placed with the cathode to Arduino output pins, and anodes to the joystick port lines. I also wanted to create a software solution that used PIO and DMA for the Read and Write components which should guarantee performance and free up the CPU for other tasks. 5 (in black and white) The only difference with rev 1. The Expansion Carrier Board simply holds the Interface Card and could also be used for any number of other projects. Sep 24, 2017 · After a bit of a wait the MyTeSed for the TSR-80 Model 100 enters the construction stage. Sinclair ZX81 Ethernet Module (7 users) This would again need a feasibility project bearing in mind the limited memory and speed of the ZX81 - although maybe an email handler would be a possibility. As well as emulating the machines themselves, various add-on interfaces are supported, including storage devices, hi-res Aug 3, 2016 · By David Stephenson August 03, 2016 AZ15, Emulators, Project, Raspberry PI, Sinclair, ZX81 Leave a Comment The final piece to the ZX81 keyboard puzzle is to get the Raspberry Pi / AZ15 to boot like it's 1981, arriving straight at the Sinclair "K" prompt after being switched on. - abaffa/zx81 ZX81 Peripherals; ZX80/81 Project - Schematics; Starting Feb 14, 2023 · Retro computing blog: Software & hardware projects for the Sinclair ZX81, ZX Spectrum and other micro computers of interest. 9 of the ZX81+38 motherboard. If you’re interested in the ZX81 then take a Feb 16, 2018 · Easy add-on Projects for the Spectrum ZX81 and Ace, was one such tome of 80s knowledge, and it's been taking filling space on book self for a couple of years. The web site and program itself include help pages. Run List Asm ZIP. Added the following tapes (total now 438): 5 Programmes Pour Jouer , 5 Programmes Pour Reflechir . In the tests I found a baud rate of 1200 is about the best that can be expected when loading BASIC files via the serial connection. 0 (Extended OCR) Ppi 267 Scanner Internet Archive Python library 0. A simple SD card reader is in sight, though not until a few challenges are met. Following on from the previous posts, in some free time this week, I butchered my ZX81 / AZ15 Arduino keyboard sketch libraries, sliced in some code for a USB host shield and beat an Arduino Leonardo into submission. ZX81 with LCD television as monitor. The board is an essential build before attempting any of the 'Easy add-on Projects for Spectrum ZX81 & ACE'. 6 is that a8 is used for the keyboard connection instead of A8'. Monday, April 08, 2024 sz81 is a Sinclair ZX80 / ZX81 emulator very much based upon the work of Ian Collier's xz80 and Russell Marks's z81 but employing the highly portable SDL and including additional functionality and features for desktop computers and portable devices. Sinclair ZX81. Using Z80ASM, the following command would do the trick: z80asm –L –o tut-tut_levels. Special features of this memory include: 8-12K on/off switch 12-16K on/off switch two banks of 8K ram available mapped 8-16K (Bank A/B switch) and 48-64K on/off switch. ZX81 Video Conditioning: describes two circuits that can be used to improve a ZX81's video output, in particular for those containing a ULA that does not generate a back porch following each line synchronisation pulse. Aug 13, 2021 · By David Stephenson August 13, 2021 Commodore PET , Computer Kits , Hardware 4 comments. A Keyboard Interface for Any Timex Computer. You can now dive deep into the legendary labyrinth and embark on an unforgettable adventure that brings the rich mythology of ancient Minoan Crete to life on your Sinclair ZX81 LCD Interface. Mar 7, 2019 · The keyboard layout is based around the 8x5 matrix format found on the Sinclair ZX81 and ZX Spectrums, which makes sense as that's what it's designed to be used with. November 10, 2022. Sometimes you've used a system variables and you need an easy reference chart to look up correct system address on the target system and move on. A Monitor Connection for the T/S 1500. This project is a collection of hardware projects for Sinclair ZX Systems (ZX81, Spectrum). The block is assembled to address 0x0000, though this is not significant. A Load/Save Switch, Test Tapes, Azimuth Alignment Revisited and Micro Cartridges. The Model 100 uses a NiCd battery to keep 32K of static RAM juiced up when the computer is powered down. The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee, Scotland, by Timex Corporation. 6 of the ZX81+38 replica board. Jun 22, 2017 · On the Model 100 side of things a couple of lines of BASIC is need to first OPEN the COM port, send a request, then download / run the files sent by the Arduino. Feb 19, 2017 · Retro computing blog: Software & hardware projects for the Sinclair ZX81, ZX Spectrum and other micro computers of interest. Cronosoft has announced the release of Minoss Knossoss for the ZX81 on Tape. TRS-80 64K PAL Colour Computer 2 Motherboard. The breakout board can be soldered directly in place, or clipped into the ZX81 keyboard header or slotted into a regular female header. ZX81 Collection, the largest online collection of Sinclair ZX81 and TS1000 games, software, books and hardware. TRS-80 Model 100 Loading From SD Card / Arduino. Over the decades his creations have stood out of the crowd and survived the test of time, remaining icons of design to this day. 5 MHz signal to synchronize the video output and it also divides the Nov 27, 2022 · Baffa-81 is a Sinclar ZX81 clone on Baffa-2 Homebrew Computer. The ULA, which is responsible for video output, uses the 6. 3. Also crucially, all key presses are detected in emulator mode, there are no dead keys combination problems such as in the "CAPS SHIFT + 9" issue discovered in PS2 mode. EightyOne is an emulator for the range of ZX home computers made by Sinclair Research (and their clones) in the 1980s, primarily the ZX80 and ZX81 but also includes the ZX Spectrum models. Jan 20, 2023 · I bought an old zx81 (paid way too much) and want to bring it back to life but discovered a few quirks and things that I need advice on. Since that time, Charlie Robson unleashed the new ZXpand+ into the ZX81 world. Note: There is a newer revision of this board which was updated to accommodate the changed layout of the keyboard connector on revision 1. A Long Cable For 2040 Printers. zip contains all gerber and drill files for the working updated and layout checked files to produce a revision 1,5 version PCB. That's it for RetroChallange 2017/10, thanks to all involved and particularly to all the other projects, it maks very varied and fun experiance. A small hole is left open to the right of the case allowing a USB lead to be plugged in when using the keyboard with a PC or MAC. This is the classic Galaxians arcade game for the Sinclair ZX81, originallypublished by Artic Computing. As can be seen from the table, the key code order is layed out in a very neat and predictable manner. Mar 10, 2019 · The ZX-Key keyboard is screwed in place with some 3mm diameter 6mm long case bolts. This entry sees the near completion of the internal retrofitting project; where some capacitors are replaced, a new voltage regulator is fitted, a lower Amperage CPU inserted and some heatsinks affixed. By David Stephenson February 27, 2019 Hardware , Keyboard , RC2014 , ZX Spectrum , ZX-Key , ZX81 , ZXKey 3 comments. Unfortunately the DRAM is soldered onto the plugin board, these needed to be Feb 27, 2019 · ZX-Key, External Keyboard For ZX81s and Other Micro Computers: Part 2. Apr 24, 2017 · Option 1: Use Some Diodes. Or how I build my own zeddy. All the major ZX81 Emulators available for use on the Raspberry Pi have SDL versions available, and SDL dosn't require an X11 windows manager. Dec 14, 2019 · Although in fairness, to call them recreations is probably a disservice. This third revision of the keyboard PCB was created to better accommodate these changes. In the last week or so another more general purpose retro network device in the form of a Serial to WiFi modem / network adapter, the WiModem232 crossed my threshold rekindling ideas around networking Feb 7, 2024 · EightyOne Sinclair Emulator. It was launched in the United Kingdom in March 1981 as the successor to Sinclair's ZX80 and designed to be a low-cost introduction to home computing for the general public. A New House for the QL. Our Arduino can then set the input to 0v when we wish to trigger a simulated push button action, and there will be no possibility of feeding +5v back to the ZXpand / ZX81. Nov 1, 2017 · I'm looking forward to finding some good uses for it outside the time constraints of the RetroChallenge and I'm certainly going to plan some future projects around it the PC-840. Some Programs Also Work On The Tandy Trs80, Commodore's Pet Timex Sinclair 1000, Timex Sinclair 1500. The circuit diagrams and stripboard layout featured can be . Jan 7, 2024 · Retro computing blog: Software & hardware projects for the Sinclair ZX81, ZX Spectrum and other micro computers of interest. Feb 6, 2022 · ZX81 Tactile Keyboard Rev. Mar 15, 2022 · The truth was that not all popular 8-bit machines had colour, sound, or good graphics, and among these limited-capability machines was Sir Clive Sinclair’s ZX81. The ZX-Key ZX81 Interface is comprised of 2 PCBs, the Interface Card and a ZX81 Expansion Carrier Board. 50 Comments. The Sinclair ZX81, developed by Sinclair Research and manufactured by Timex Corporation in Dundee, Scotland, was the first home computer sold in the United States for under $150. 2021 sees the release of a significant update to the standalone kit in the form of the Mini PET RAM Memory Expansion. 9 of the ZX81+38 replica board. Aug 21, 2016 · The Version 2 removes the kludge of keyboard debouncing, and now thankfully we have a keyboard that functions just as well as that on any self respecting ZX81. For Version 2 of the IO board I selected the 8255A, as it's pretty well documented, and as a bonus it made an appearance in a ZX81 IO board designed by A. Mar 27, 2022 · The ZX81 has a clock oscillator made from a 6. Two MyTeSeds, one attached to a Model 102 and the A tribute repository for the Sinclair ZX81 homecomputer. Retro computing blog: Software & hardware projects for the Sinclair ZX81, ZX Spectrum and other micro computers of interest. Booting won't be measured in seconds (actually it comes in at May 8, 2020 · Updated the ZX81 Tape Converter to provide a decent GUI front end. Aug 13, 2016 · In Part 1, we setup the AZ15 to boot into a kiosk mode that relied on X11. Housing the ZX-Key Lite Keyboard in Aug 17, 2017 · As in the previous version (blog entry Using SD Cards with the TRS-80 Model 100) a MAX323 IC handles the RS232 to TTL serial conversion. Of course, building a circa-1980-something computer from new parts is a bit Aug 29, 2023 · Building a new ZX81 Computer. Publication date. Option 2: Use a 4066 IC bilateral Switch. ) - 64K DRAM board for the TS1000, TS1500 or ZX81. 2. 1982. g. 9 of the ZX81+38 motherboard changed the layout of the keyboard connector. The new board is more about providing choices, more than a fundamental redesign. A huge number of expansion RAM packs were produced for the Sinclair computers. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Yes is the old leaky soldered-in NiCd battery curse of old computers. The display of a full 320 by 240 image in real time (e. A Monitor Adapter for the T/S 1500. Oct 31, 2023 · Breakout Board Projects Home Automation zx81+38 computer. sz81 is a Sinclair ZX80/ZX81 emulator very much based upon the work of Ian Collier's xz80 and Russell Marks's z81 but employing the highly portable SDL and including additional functionality and features for desktop computers and portable devices. While its successor, the Sinclair Spectrum, got the nation playing computer games, the ZX81 was the tipping point that turned the home computer from nerd Saved searches Use saved searches to filter your results more quickly Jan 3, 2020 · The ZX-Key Minstrel adapter is really just a simple breakout board for the standar ZX-Key keyboard. Most (I'm not going to say all as there are weird regional variances) LCD TVs still have Composite video ports. zxspecreckeyboard_20240121. The ZX81+38 is a clone of the Sinclair ZX81 home computer that replaces the ULA found in the original with standard logic ICs. This version has been adapted to work with hi-resolution display interfaces which are mapped to 3000h in RAM. it works perfectly - I had 10 made and so far I have Jun 10, 2017 · As previously mentioned (in Part 1: USB Mouse For The ZX81 And ZXpand ), the USB mouse interface relies on normal Atari digital joystick inputs as found on the ZXpand. Posted on January 3, 2022. As the supply of genuine retrocomputers dwindles and their prices skyrocket, enthusiasts are May 29, 2021 · May 28, 2021. asm. Sep 20, 2016 · Retro computing blog: Software & hardware projects for the Sinclair ZX81, ZX Spectrum and other micro computers of interest. zip. Read more →. Essentially the projects light pen functions as a light detector that doesn't detect CRT scan line progression. MaxDemo) uses approximately 90% of the available CPU clock cycles. 5 MHz clock circuit is fed directly to the ULA (IC1 - SINCLAIR COMPUTER LOGIC) on pin 35. Arranged in a row on the plugin board, are eight 8k MB8264A DRAM chips, these provide the systems total of 64k. The ZX-Key Keyboard Mounted on the Prototype Keyboard 'Starter' Case. The within this repository are intended soley for personal or educational use. Nov 29, 2020 · The ZX-Key Lite version can always be updated to a Full / Classic at a latter stage by installing the missing components and switching a jumper wire. 37 TIMEX 1000/Sinclair ZX-81 Programs for Home, School & Office. Dec 31, 2015 · Retro computing blog: Software & hardware projects for the Sinclair ZX81, ZX Spectrum and other micro computers of interest. That means, it can be built with all parts still readily available today. The end result a fully working Recreated ZX Spectrum keyboard. Mostly the build went smoothly, mostly being down to one misguided assumption in turn inducing lot of time spent waiting. Be sure to check out Rods video review of the ZX81 TuT-TuT Demo Feb 13, 2019 · With the basic idea of the keyboard at hand, I needed a way to connect it to a ZX81. Victor Trucco 64K Dynamic RAM (John Oliger Co. In order to undertake the builds presented within Easy add-on Projects for the Spectrum ZX81 and Ace, an initially requirement is the construction of an Address Decoder board, itself Feb 4, 2018 · The UDG for ZXpand is designed to be used in conjunction with memory expansions supporting the WRX extensions / modifications. 20 Program Listings On The Zx81. For the output wires you have a choice to make, either integrating a small video jack (3. For many, that was enough. For normal ZX81 users you’ll notice the drops start at random locations in the top half of the screen. Aug 18, 2023 · Its layout incorporates a three row hole arrangement on the printed circuit board, with ZX81 BUS 1a duplicated twice, offering the flexibility to house either two-row expansion headers or card slots – you know, the same kind that snugly attach to your trusty ZX81. The command line / serial switches have, thanks to the changes, slimmed back down. Option 1: An LCD TV. Sometimes when you've written an application for the ZX81 or ZX Spectrum you wish to port it to the other, or even back to the ZX80. Recreated ZX Spectrum Arduino / Leonardo & USB Host Shield 2. me. With this comes some potential options, in particular a TTL serial port has been included on the . Working out where the light pen is on the screen is left entirely up to our BASIC programs. asm’ and make sure to write a label file, so you can work out how big the binary block is. One of the major goals has always been to take the project to the next level and launch a full ZX81 work alike. SInclair, ZX81, Electronics, acpc. There is a 16 KB RAM expansion pack which addresses this, but because it's about half the size of the computer itself, it's not very practical and easily disconnects, instantly crashing the computer. 30 Hour Basic - ZX81 Edition. If you think the Spectrum Next looks gorgeous, it’s all his doing. Also of note, the case has a gentle 2 degree slope from front to Oct 2, 2016 · Arduino Liberates the Recreated ZX Spectrum. Sinclair ZX81 Dark Screen Fix. Apr 16, 2023 · All three of these chips are period correct for the ZX81, in production and available of the shelf today (at least in 2023). Modern memory boards such as the ZXpand (+) and the ZXblast support this natively. com Mini PETBack in 2020 Tynemouth Software released the Mini PET onto a largely unsuspecting retro computer kit appreciating public. The output of the 6. 8 Mar 5, 2021 · As a pet project begun out of nostalgia for the machine, Palser attempted to recreate the ZX81 as a human interest project that became a living tribute to the ZX81’s appeal – with the words of May 12, 2020 · First, assemble the source file ‘tut-tut_levels. Use of the Z80 emulator originally written for xz80 by Ian Collier, plus optimisation of the ZX81 memory access, display and plot routines allows the emulator to run at 100% of real time speed. Jun 14, 2023 · We have to admit liking this project a lot, in fact we’re even tempted by a set of these keycaps for a regular keyboard just for old time’s sake. bin tut-tut_levels. This Extender knows how to cater to your every expansion whim. Note: Revision 1. Jan 7, 2024 · By David Stephenson May 25, 2024 Games Minoss Knossoss Sinclair Software Tut-Tut ZX81 Leave a Comment. Sep 4, 2015 · So some early clarifications, the project isn't about re-engineering a ZX81 from the ground up, it's not even going to be about re-creating the exact look of the original, it's simply about creating something with passing physical appearance resemblance and finding a (non)practical use for ZX81 like computer in a case. ZX-Key Lite: Board Upgraded to Classic and attached to a Minstrel ZX81 Clone. The aim of the game is to shoot down the invading aliens before they destroy you. Jul 25, 2018 · This is to be found on a plug in board hovering above the motherboard, with some cardboard shielding over it. The cleanest option being the second. I wanted to create a 16K RAM Pack for my Sinclair ZX81, so started development using my favourite MCU, the Raspberry Pico. Provision has been made for mounting it firmly to the Minstrel, held in with a bold. Added a catalogue scan for JRS , and fixed the links for catalogue scans for Quicksilva and Software Farm . Collection. And, of course, I've finally integrated joystick support and rudimentary sound for those fortunate enough to be using ZON-X sound cards and Aug 28, 2016 · By David Stephenson August 03, 2016 AZ15 , Emulators , Project , Raspberry PI , Sinclair , ZX81 Leave a Comment. May 12, 2018 · Retro computing blog: Software & hardware projects for the Sinclair ZX81, ZX Spectrum and other micro computers of interest. For Chroma users, it adds different drop shades that are closer to the original. This is a PCB for a cheap and easy to build keyboard, designed to go with revision 1. Luckily it's quite easy to upgrade the memory of the ZX81 to 16K An industrial designer of unparalleled talent, Rick’s seminal works include the ZX80, ZX81, ZX Spectrum, Plus and QL. Feb 3, 2017 · To start, it's simply a matter of attaching the input wires to the back of the ZX81 circuit board: red wire +5V to ULA pin 40, the black wire 0V to ULA pin 34 and the yellow wire to video In at ULA pin 16. 0 Sketches. Launched in England on March 5, 1981, the ZX81 was designed to be a low-cost introduction to home computing for the general public. 5 MHz ceramic filter identified as X1 in the schematic below. by. gd mn xc wu md iv gh pb uy wp