© Brooke Clarke, N6GCE 2000 - 2024

also see HP Rocky Mountain Basic (RMB) instrument controllers (computers - calculators)
USB vs. PS/2 Keyboards & Mice 
Tube Circuits
    Operating System
    ASR33 TTY 
    ADM-3A Glass TTY Kit
    Sirus Cybernetics VGA-1
    Ferro Resonant Power Transformer
    Intel 2102 Static RAM Memory
    Audio Cassette Tape Data Storage
    8" Floppy disk DMAF1
    5 1/4" Floppy Disk 
    3.5" Floppy Disk SSSD 
    Don Lancaster TV Typewriter Kit
    Lear Siegler ADM-3A Dumb Terminal (Glass TTY) Kit
    TI 810 Dot Matrix Printer 
    Epson FX80 Dot Matrix Printer
    Wood Cased Version
Home Brew Computer Club
    Computer called the Apple
    Motorola Assembler and Editor
    San Francisco Computer Show
    Tiny Basic
Radio Shack Color Computer
What's in a Name?
Memory Chips & Programmers
Byte Shop
    HP 9100
    HP 35
    HP 41
    HP 48G
    HP 80 Series
    TI Speak & Spell
        Power Supply
        Miniature Electronic Calculator (TI-1400)
        Keyboard Patents
    Federal Screw Works Votrax
Magnetic Storage
Curta Calculator

USB vs. PS/2 Keyboards & Mice

March 15 2008 - I have a KVM switch connected to the HP 4395A, an HP Pavilion computer and my working computer via PS/2 and 15 pin Video cables.

For the last two days I've been trying to replace the mouse (sometimes does not send signal even though it "clicked", or sends two signals for a single click) and keyboard (some keys don't always send a signal).

First tried a "Wireless Desktop" thinking it would be nice to eliminate the mouse wire.  There were two problems:
1) there is only one common unit with a USB connector.  Plugging that into a USB to PS/2 adapter allowed the mouse to work, but since nothing was plugged into the keyboard socket on the KVM switch, not keyboard.  OK, my plan then was to just get a wired keyboard and keep the wireless mouse.  But after a while it was clear that the mouse hangs up when the computer CPU is working hard OR if the common unit is near almost anything electronic, like a WRT350 wireless router or a Maha AA battery charger.  So back to wires for both keyboard and mouse.

Next tried wired Logitech Wave keyboard and Microsoft Comfort Optical Mouse 3000.  The mouse came with a single piece green PS/2 to USB adapter and plugged right into the KVM switch and worked.

The keyboard did not come with an adapter, but I already was using one of the green ones identical to the one on the mouse port so tried it.  No luck the keyboard will no communicate with the computer.
A SOLUTION:  Instead of just rebooting the computer it was powered down then brought back up.  It found the keyboard and now it's working.

Tube Circuits were First

During W.W.II there was secret work in the UK and US that used tubes to speed up the process of cracking German ciphers.  Later tubes were used in counting circuits which led naturally to tube circuits that could do mathematical operations.  This led to general purpose computers based on tube technology.

I don't know if there were computers built using descrete transistors since very shortly after the transistor was invented Fairchild started making RTL digital logic ICs and TI started making TTL logic ICs.  Both of these were used to make all kinds of things including computers.

If tubes had not come about then relay based logic might have been the first technology used for a general purpose computer.

Intel is just down the road from Fairchild in Silicon Valley.  There is a street in Santa Clara, California ( a couple of cities away from Mountain View where Fairchild started) that has liquid Nitrogen pipes in the street and is a utility like water and electric.


A microprocessor is a computer on a chip.  It has: The Intel 4004 was the first chip that had general purpose capability.  It was made for use in a hand held 4 function calculator and/or for use as a traffic light controller.  It used 4 bit words, enough for numbers but not enough for 8 bit ASCII characters.  The 8008 then 8080 chips were 8 bit data word chips.
The microprocessor works like a Turing machine (Wiki) in that it stores data and instructions in the same memory (Wiki: Computer architecture).


The microcontroller is a much more modern part.  Instead of having the classic address and data buss I/O pins it has register pins that can be digital I/Os, analog inputs/outputs, serial buss signals, or other things that relate directly to hardware interfacing.  These are typically used in embedded control applications not for general purpose computing.  The PIC line from Microchip is a typical example (16F88).

The PIC family of microcontrollers uses the Harvard architecture (Wiki) where there are separate memories for data and instructions.  This not only prevents reading data as instructions or storing data in locations that are for instructions but also makes for faster operation.


Digital Message Device (Black no label)
PSG-9 Message Terminal (Computer)
Panasonic CF-28 Toughbook Laptop Computer
Black Diamond (company external web page) - Modular Tactical System (MTS)


This was my first personal computer.  It came as a kit and there was no software available when I got it.  It came with the Motorola 6800 pocket hex instruction card.

The 6800 has a Von Newman architecture (Wiki) both in terms of software and hardware.   That's to say the RAM contains both instructions and data and the hardware uses memory mapping for the hardware interfacing.  This is different than the early Intel microprocessor chips that had separate electrical terminals for external hardware.  It's also different from the Harvard architecture (Wiki) used with the PIC micro controllers (PC6, LED1PC2, PICpkg, PIC16F88, PClock, Precicion Clock #4).

The 7 SWTP mother board slots each have the same 50 buss lines.  The mother board includes address decoding for the 8 I/O slots.   This means that the I/O boards do not need address decoding since they are already memory mapped.  Note the early Intel based home computers, like the Altair 8800 (Wiki) used the "S-100" buss that had twice the number of connections and no address decoding so all the cards had 100 connections making them much more expensive.

YouTube:  The 8-bit home computer from 1975 you've never heard of, 30:12, March 26, 2022 -
deramp5113: SWTP 6800 - Teletype -
SWTP 6800 Computer
Fig 1 Shown with front and back trip strips just sitting in place.
The expanded metal top/side cover is not shown.
SWTP 6800 Computer
Fig 2 The silver can cap on the right with white line cord
wiring reasonates with a transformer winding.
Fig 3 MP-B Motherboard
SWTP 6800 Computer
Fig 4 50-Pin RAM
Notice that the2102 static memory chips are soldered
directly to the board.  Sockets were not reliable and so
caused problems.
I had a similar problem with plug-in hard drives.
i.e. the socket caused a disk crash.
SWTP 6800 Computer
Fig 5 50-Pin RAM
SWTP 6800 Computer
Fig 6 50-Pin RAM
This is the SWTP RAM board,
the others are after market.
SWTP 6800 Computer
Fig 7 50-Pin MP-A CPU
SWTP 6800 Computer
Fig 8 50-Pin DMAF1 Dual Drive DS Floppy Disk I/O
SWTP 6800 Computer
Fig 9 MP-S Serial
SWTP 6800 Computer
Fig 10 MP-T Timer
SWTP 6800 Computer
Fig 11 MP-LA
SWTP 6800 Computer
Fig 12 Sound (resistor ladder & LM380)
SWTP 6800 Computer
Fig 13 MP-L Parallel Printer
SWTP 6800 Computer
Fig 14 Dual YE-Data 8" Floppy Drives
SWTP 6800 Computer
                  Dual 8" Floppy Drives
Fig 15 Audio Cassette Data Interface
SWTP Audio
                  Cassette Data Interface
Fig 16 Works with two cassette drives,
one for writing & one for reading.
SWTP Audio
                  Cassette Data Interface

I started with the Motorola 6800 in a SWTP (South West Technical Products) kit.  The kit came with NO software and there was no software on the open market.
It did come with the folding Motorola wallet size machine language instruction list.  I learned how to program directly in hex machine code.  This was difficult because if you added or subtracted an instruction inside a loop you need to recompute the loop jump distance.
Motorola folding Pocket 6800 Instruction Set Card (Issue B):
Motorola folding Pocket
                6800 Instruction Set Card (Issue B)
Motorola folding Pocket
                6800 Instruction Set Card (Issue B)
Motorola folding Pocket
                6800 Instruction Set Card (Issue B)
Motorola folding Pocket
                6800 Instruction Set Card (Issue B)
Motorola folding Pocket
                6800 Instruction Set Card (Issue B)

Motorola folding Pocket
                6800 Instruction Set Card (Issue B)

Teletype Pocket Card with 8-level punched tape data format - you can read paper tape by eye  Front Side - Table Side (at 2X magnification)
Between bits 3 and 4 there is a row of small sprocket holes.  The special  USASCII (X3.4-1967) characters are: Motorola published the M6800 Microprocessor Applications Manual, an 8.5 x 11" book about 1.5" thick.  It contained sample code for many applications that may have been parts of a point of sale terminal.  This was a handy reference to learn many "tricks of the trade". My copy has seen a lot of use.

21 Aug 2004 - Shortly after getting my SWTP 6800 kit and building it I started learning Motorola assembly language from the pocket card and the 81/2 x 11 x 2" book that included a lot of source code and schematics.  Note there are only 2 buttons on the front of the SWTP 6800 On-Off and Reset.  When either of them is activated the 6800 either goes to a cold or warm start address in the operating system ROM and boots itself.  The 6800 has an instruction that is a relative 8 bit  jump and it was this instruction that allowed Microware to create their Real Time operating system ROM chip to replace the stock Motorola ROM used in the SWTP 6800.  Motorola, AMI and other vendors were big on the idea that you could write code that could be:
The big advantage of Re-locatable Recursive code is that the routine does not need to be re-written when it's used in a different location allowing a library of routines to be built and called as needed.  When the 6800 uP came out it was common to write self modifying code (it is a Von Newman architecture where code and data share the same address space).  The PIC uC chips use a Harvard architecture where code and data spaces are separated thereby forbidding self modifying code.

This RT68 operating system evolved into OS-9 which was a very sophisticated op system with features that even today (OS-9000) are great.  It depends on the ability to have Relocatable Recursive code.

I remember when the 6809 came out in the Color Computer and I went to a local Silicon Valley meeting to see what some hackers had found.  One of the most interesting things about the 6809 as implemented in the CoCo was that although the operating system/Basic language was stored in ROM, it was moved into RAM for execution.  This means that other operating systems, I used OS-9 on my COlor Compugter, could be loaded and run.  The demo was to display on the TV screen the machine code in a dynamic way, page after page.  A Motorola app note for the 6809 contained the schematic for the CoCo.

Motorola had a program where if you contributed some 6800 assembly code to a pool of code you would be allowed to get code for the pool for free.  This pool of code was analyzed by Motorola and the 6809 had a more orthogonal instruction set as a result.  The 68000 also had a long relative jump making it easier to write relocatable code.  The 6809 probably had the long jump.

The Altair kit had a front panel with a lot of switches and lights that were used to manually define a loader program so that the computer could be started, very time consuming.  The SWTP front panel has just two buttons: Power on/off and Reset.  It contains a ROM chip with the bootstrap program, a simple debugger, and a way to enter programs in Motorola "S9" format.

The Altair kit has a mother board that has a 100 pin buss (with a hard to get connector) and no chips.  Each plug-in board needs to decode the full buss making the boards cost more than needed.  The SWTP has two buss structures, one "SS-50" 50-pin for RAM, DMA (Direct Memory Access), etc. (that used easy to get Molex type connectors) and one narrow I/O buss where the motherboard has already decoded some addresses to allow a simple I/O card to be used.  Many years later the IBM PC followed the SWTP lead using a separate I/O buss.

Operating System

I replaced the Motorola ROM with the first product from Microware called RTOS (Real Time Operating System).  The key to this was that the 6800 had instructions to allow jumping to an address RELATIVE to the current program counter.  The Intel chips only had instructions that pointed to fixed addresses.  The availability of a relative address instruction allows code to be written in modules that could be relocated in the address space.  Relocatable code is much easier to use than code that must be loaded in a fixed location. Reentrant, Recursive, and some other R words characterize much of the code written for Motorola chips at that time.

Later there was a Flex Disk Operating System.  I think it supported a flavor of Basic so you could write programs in a much easier way than using hex or assembly.
FLEX User Group -

ASR33 TTY (Automatic Send Receive)

This is a Teletype (brand name) machine that is 8 level (meaning that it worked with 8 bit data).  There were a lot of surplus 5 level machines available that would not work with 8 bit microcomputers.  The neat thing about the ASR33 was that it could do four things: The interface was 20 mA current loop with ASCII data format.  There was an RS-232 I/O card for those who could afford an acoustic coupled modem.  (At that time AT&T had all of the phone system and it was a crime to connect directly to the phone lines.)

It could use pin drive or friction feed paper.  Friction feed allows the use of lower cost paper in rolls with no sprocket holes.  The nicer paper that has a perforation every 11 inches needs to have sprocket holes so that you can do a "Form Feed" to get to the top of a page.  You could get multipart paper for the ASR33 since it was an impact printer.  The printing head is a cylinder that moves up and down and rotates to get to the character needed.

100 Words per minute is 500 characters per minute or 8.333 characters per second.  In 30 minutes you could read 15,000 characters and the tape would about about 125 feet long.  If wound on a 1" core the paper tape spool would be about 5" in diameter.  I had a drafting 115VAC powered electric eraser and an attachment with a flat face and some pins that would wind up a 100 foot tape in under a minute.  Some care was needed to not tangle the tape and avoid a paper cut.

The one illustrated at has a rotary dial and built in modem that was not present on mine.

TTYPUNCH: punch a perforated ITA2 TTY tape -

 B    R  O   O   K  E        C   L  A   R   K  E        H   T   T   P   ://                      W  W  W  .               P   R  C   6   8   .               C   O   M

 There's something wrong with the TTY Punch program.  When a character that's not in it's alphabet something strange happens.  The input was 34 characters and the output is 40 characters.

Also see:
HP 2748B High Speed Rack Mount Paper Tape Reader -
Tape-ARD® Paper Tape Key Punch Model 173A
Telegraph - Teletype
KD-100 Key Tape Disintegrator

ADM-3A Glass TTY Kit (Wiki)

The PCB is on a diagonal which is at the hing line between the top (white) and bottom (Blue).  In the kit version that PCB was filled with ICs.  There was a later version with the same size PCB, but it had maybe a couple of ICs and the rest was just blank space.

Sirus Cybernetics VGA-1 50-Pin Printed Circuit Board

This was part of a kit to add a VGA color display instead of using an I/O board to drive a TTY machine (real or glass).
The PCB is dated 1980 and is raw, i.e. no parts have been installed.  Maybe it required an expensive chip.

Ferro Resonant Power Transformer

I replaced the stock power transformer with a ferro resonant model.  This involved also adding an oil filled cap that connects to an extra winding on the transformer.  The idea is that the resonant circuit rejects narrow spikes and dropouts and also supplies some energy for short brown outs.

Intel 2102 Static RAM Memory

The large type card for the SWTP computer could be purchased that were all covered with 2102 memory chips.  They made a point of NOT using sockets because the reliability of the socket was lower than the chip.
2 pins for power, 4 control pins (DO, DI, /CD and R/W) and 10 address pins for a total of 16 pins.  It has a capacity of 1 bit x 1024 = 1k bits.

AC-30 Audio Cassette Tape Data Storage

The next innovation was a box made by SWTP that allowed storing data on audio cassettes by means of tones, very similar to the 1200/2400 Hz modems that were starting to appear.
Wiki: Kansas City standard.  This required the SWTP AC-30 interface box.  Two common portable cassette tape recorders and three cables going to each recorder: Mike, Earphone & Motor control.  You need two recorders so copy from one to the other.  While it can be done with one recorder it takes much more time.

8" Floppy disk DMAF1

This was a big improvement on the cassette tape system.  The 8" data transfer rate (500 k bits/sec: IBM 8-Inch) was too high for the microcontroller to bit-bang (Wiki), so a wide SWTP card with DMA (Wiki: Direct Memory Access) was used to move data directly to/from RAM to the floppy disk.  Motorola has a chip (6844?) just for doing the DMA operations that could also be programmed to move data in the RAM space.

The early 8" disks were single sided and later there was a double sided 8" disk and SWTP packaged two of these side by side.  You need a way to copy from disk to disk and using two drives is much easier than buffering the data and manually installing and removing disks.  The same applies today to DVD and Blueray disks.

YouTube: CouriousMarc:

AFAICR the data rate was 500 k bits per second or 2 microseconds between bits or 16 microseconds between bytes after a serial to parallel chip converted the data. 

My next door neighbor was Reed Anderson (Wiki) founder and president of Information Terminals Corp (formerly Anderson Jacobson Inc (Patents 1971 - 1984) (Wiki)), maker of telephone modems and floppy disks (later renamed Verbatim).  He told me about the 8" double sided YE-Data floppy drives.   I bought his 8" disks and talked to him about what drives were available.  One day he brought Victor Borge (Wiki) to my house so that he could see a home application of the floppy disks.  Later Victor did commercials for Verbatim disks.  Reed Anderson was a very class act and gentleman.

YouTube: CuriousMarc: More about 8" floppies: recovering data from odd diskette formats I didn't even know existed!, 15:59 -

5 1/4" Floppy Disk

Replaced the 8" disk with a pair of 5-1/4" disks because they were smaller and ran at half the speed allowing for bit-banging, thus greatly lowering the cost.  These had a slower data rate so the microcontroller could handle the data without needing the complexity of DMA.  At 250 k bits per second or 32 microseconds between bytes there's enough time to bang bytes with a 6800 chip.

3.5" Floppy Disk SSSD

Replaced the 5-1/4" disks because of even smaller size and more rugged because of the hard plastic shell.  Replaced the use of tape for write protection on the 8" and 5-1/4" disks and instead used a sliding plastic door that could be read by an optical sensor.

These started as Single Sided Single Density and had the same interface as the 5 1/4" Floppy disks.  They progressed through Double Sided and finally Double Density.  (I paid $50 for a box of 10 DSDD disks from HP when they were introduced.)

Don Lancaster TV Typewriter Kit

This is a way to use a standard NTSC TV monitor as a display device.  The problem is that with a TV bandwidth you can not display a line of 80 characters.  I have the book but didn't make it.  Prior to this the main interface was a Teletype ASR 33.

Lear Siegler ADM-3A Dumb Terminal (Glass TTY) Kit

This is just a keyboard and CRT to replace the TTY keyboard and paper printer (but not the paper tape punch & reader).  24 Rows by 80 Columns.  Punched cards have 80 columns so the display works for input and output of data that may have been formatted for cards.  It has no graphics capability, only alphanumeric text. Came as a kit that uses what seems like a hundred ICs.  Later Glass TTY terminals used only a handful of custom IC chips and cost much less.

You could do graphics the same way they did for the Teletype machines, i.e. by printing characters in a graphics pattern. A period has a small amount of ink in a character space while a letter M has a lot of ink.  It was a tedious process to make up a still image in this way but was popular around Christmas time.

TI 810 Dot Matrix Printer

This floor standing dot matrix text only printer takes fan folded 132 column paper and has pin drive.  A later version had graphics capability.  I seem to remember that is cost something like $2,000 back when a dollar was worth something.

Epson FX80 Dot Matrix Printer

This pin drive printer takes 8.5" wide paper and has graphics capability.  Mine has a special add on chip that increases it's capability.

Wood Cased Version

I installed the boards into a custom wood case rather than keep using the factory SWTP case.  Note I seemed to always have the cover off the SWTP case in order to get access to do hardware hacks.

Home Brew Computer Club (Wiki)

The meetings were held at the auditorium at the Stanford Linear Accelerator Center (SLAC) on Page Mill Rd. in Palo Alto, a few minutes drive from where I lived in Los Altos Hills.

The auditorium had each row of seats about 1 foot higher than the row in front so that everyone could easily see the black boards, speaker, etc.  I think it's built on the side of a hill.

The format would be:
At one of the meetings a couple of kids with greasy hair had a card table at the auditorium door showing off their computer on a board that had a built in video display, built in basic as well as a tape interface, they called it the Apple.  Many of the Silicon Valley microcomputer types were attending these meetings.

It was here that Tom Pitmam (Wiki, Itty Bitty Computers) found me.  I had a SWTP 6800 computer and a Model 33 Teletype.  At the meeting I got two paper tapes, one for a 6800 editor program and the other for a 6800 assembler.  I had already coded a hex a disassembler that would read Motorola 6800 machine code and print out a pseudo assembly listing.  This allowed Tom and myself to figure out how to use the undocumented paper tapes.  This allowed Tom to write Tiny Basic (Wiki) based on an article in the Computer Journal about a basic language with a metaphor about layers of a onion.  Because I was interested in using my SWTP 6800 computer to interface hardware one of the things I asked for were instructions for PEEK and POKE to allow looking at or modifying any memory location.  This was a capability of the HP RMB language.

At this time I was going to the Home Brew Computer Club meeting at the Stanford Linear Accelerator Center (SLAC) auditorium on Page Mill Road in Palo Alto.  Inside they would have a guest lecturer, and time for questions, wants, etc. then a Random Access time when you could go to someone with a question, want, etc. and talk one (or many) to one.

Computer called the Apple

There would be an exhibit at the entrance door.  One time it was a couple of kids showing their computer, on a card table, that was all on one board, included a basic language in ROM and had a TV interface, they were calling it the "Apple".  I think it used the 6502 chip that was very similar to the 6800 but with some enhancements (color display and sound).  This was a raw board, no cabinet.

Motorola Assembler and Editor

At another one of the Home Brew Computer Club meetings someone had the paper tapes for the Motorola Editor and Assembler (that's 2 separate programs).  And I got the tapes, no documentation or anything else.  By this time I had written a source code generator program.  It would read a machine language paper tape and print out the source code and machine language mnemonics.  This allowed me to reverse engineer the editor and assembler to find out how they were handling the I/O.  It turned out they were written by a professional and had a header where the I/O ports were defined.  It was a simple matter to reassign the ports to match the SWTP TTY I/O port.  This was a great tool, now you could write code without worrying about recomputing loop jump addresses.

Later a generic assembly language became popular called "C".  "C" is a low level language it's just a little bit removed form assembly language where the language is very closely tied to the registers of the target chip.

I think most (all?) of the computers that use the 68xxx chips use the same method so it's straight forward to have one box emulate another box.
A very high level language is LabVIEW by National Instruments.

San Francisco Computer Fair (Wiki)

There was an annual show that was for small home type computers in SF.  Jim Warren (Wiki) put it on and used roller skates to cover the large area of the show floor.  There were papers given and exhibits.  Those two kids with their Apple computer had a booth.

Tiny Basic

Tom Pittman wanted to develop a version of Tiny Basic as written up in Doctor Dobbs Journal.  He used my computer by working into the wee hours for a number of days.  When he was done I got a copy.  I also asked him to include hooks (PEEK & POKE) to allow the language to bang bits so that it could be used to control hardware, not just be used as software.

Radio Shack Color Computer (Wiki)

CoCo Computer
Multi Port Adapter
Radio Shack TRS-80
                  Color Computer CoCo 6809

This was based on the Motorola 6809E Chip.  The Microware OS9 operating system was available for this computer.  It used a color TV as an output device and can be used to make titles for video tape.  Motorola has an app note on the 6809 chip with the design of the COCO.  This was a low cost computer with a lot of capability.

The way the CoCo was made the operating system is stored in ROM, but at power on it is transferred into RAM.  This means that you can write code to replace the operating system.  Since the standard TV display is just a part of memory you can change the start address of the display map and that allows you to look at any RAM address dynamically.

There was a company in Sunnyvale that was buying the COCO from Radio Shack, removing the case and embedding it into a commercial product that was involved in routing telephone calls (like to a doctor's office after hours).

When the 6800 chip came out Motorola had a firmware program where if you donated some code  you could access their 6800 library of other donated code.  They analyzed that code and based on what they found improved the orthogonality of the 6809 code as well as that for the 68000 series.

Multiport Adapter

By plugging this into the game slot, you could have 4 game slots available.  There were a number of after market products that fit the game slots, like a Glass TTY type display that would drive a wide bandwidth monitor to allow 80 characters per line which is more that you can get with a TV display.

One of the cards in the display adapter is to drive a CRT monitor so that I can display 80 characters in one line (way more than the TV display allows).

What's in a Name?

Some learning experiences got me thinking "What's in a Name".  

First when getting the Motorola 6800 Editor & Assembler to work on the SWTP 6800 computer it was discovered that at the beginning of the program there was a jump table to the hardware I/O address.  (Motorola 6800 and 68000 series hardware uses memory mapped I/O unlike the Intel 8080 series CPUs)  So by simply making one change for each of these the software would run on the SWTP computer.  It was not necessary to go through all the code making changes.

The HP Diskless Node Unix Workstation could be used as an HP Rocky Mountain Basic computer.  These sold for a lot less than products advertised as "RMB Workstations".    But the boot ROM in both the Diskless Node and the RMB Workstation are very similar, allowing the Diskless Node to load the RMB Workstation software.

Atari had a game computer that was Motorola 68000 based.  It was possible to install Apple MacIntosh ROMs in a game cartridge and when the game machine booted up is was a Mac computer.  I started looking into using the Atari as a RMB workstation, but didn't get a round Tuit so never tried it.


With the advent of electronic counting the older Veeder-Root mechanical counters (like a car odometer) or counters that used incandescent bulbs were not fast enough.  So there was a need for a visual display that could keep up with electronic counting needs.
The Dekatron and the Neon lamp were the first electronic counter displays I remember. See the story of breaking the 4-rotor Enigma machine by NCR.


RTL logic Binary Counter Lamps for output
This is a binary counter made using Fairchild RTL ICs.  I  lived in Mountain View, California at this time and Fairchild started out on Ellis St.  A local phone call would get a BIG three ring binder full of RTL data sheets.  Some surplus stores sold seconds that did not have labels but instead a color stripe and these were lower in cost than the official parts.  One button increments the count and the other is the reset.

RTL Johnson Counter
          prototypeThis is a prototype Johnson (Twisted Ring) Counter (Wiki).  The lamp indicates a divide by ten, i.e. is the carry out.  A push button mounted in the drilled steel practice panel increments the count.
A Johnson counter may be the fastest counter you can make since the toggle rate for each IC is much lower than the input unlike a straight binary counter where the input stage is toggled at the input rate.


HP AC-4A qtr view A group of 10 NE-2 Neon bulbs were arranged in a row with a photographic film overlay showing the Arabic digits 0 through 9 in a straight line.  This AC-4 used 4 dual triode vacuum tubes.


RTL Johnson Counter driving Nixie TubeA Nixie tube (Wiki)  has the Arabic digits formed by shaping wires and they are all stacked front to back inside a Neon filled glass tube.  You only see the digit that's on. 

I made a Johnson ring counter using 5 Fairchild 923 RTL Flip-Flops (Semi Museum) on one Printed Circuit Board (on the right).   A decoder PCB has RTL gates on the back.  These only need to have two inputs since decoding a 5 stage Johnson counter is much easier than a binary counter.  Each gate output drives high voltage transistor that turns on a Nixie element.  The artwork was done using black tape on plastic drafting sheets at 4 X life size.  A blueprint shop then makes a high resolution negative that's life sized.  A PCB etching house makes the single sided board.

The metal shop at Aertech had some machines that engineers were allowed to use (mess up) but most of the machines were strictly off limits and rightfully so.  The manual punch press and sheet metal brake were fair game.  So it's possible I made the sheet metal part or that a machinist did it in the late 1960s, or whenever RTL was introduced by Fairchild.  The sheet metal would hold a two digit counter.

Nixie Tube Patent

2138197 Electric discharge lamp, Pressler Hermann, Richter Hans, Radio Patents Corp, 1938-11-29, - but not different symbols, this is more like a neon sign.
2142106 Signaling System and Glow Lamps Therefore, Hans P. Boswau, Jan 3, 1939, 315/184 ; 235/23; 313/245; 313/250; 313/257; 313/582; 315/167; 315/170; 315/299; 315/324; 315/DIG.1; 377/113 - looks like Nixie tube, but  has a problem described below
2618760 Glow tube anode construction, Robert D Hancock, Charles R Williams, Glenn E Hagen, Chris S Andersen, Northrop Grumman Corp, 1952-11-18 - the only citation is to 2142106. "It is, therefore, an object of the present invention to provide a means whereby the distance between the cathode and anode of a multiple cathode ionic glow tube or the the read-out type is maintained nearly uniform, over` the entire length of the cathode, and for all of the cathodes."


One of the first solid state display devices was the Light Emitting Diode.  A relative had a Bulova Accutron (Wiki) watch with an LED display, but the problem was that it took a lot of power and used up batteries quickly.  Later TI sold an LED wristwatch and when the battery went dead it was cheaper to buy another watch than have someone replace the battery which required special tools and skill.

7 Segment Display (Wiki)

The Numitron: An obvious idea that wasn't very bright, 23:20 -
683133 Interchangeable electric display apparatus, George Lafayette Mason, Mason Monogram Co, 1901-09-24
974943 Illuminated announcement and display signal, Frank W Wood, Charles Cory & Son, 1910-11-08, -
2878418 Miniature filamentary numerical display, Alan R Garfinkel, Biagio A Spinelli, Munt Irwin, Sperry Rand, 1959-03-17, -
3564325 Display device including a point image, Richard Arthur Bonnette, Norman Lee Lindburg, RCA, 1971-02-16, - Numitron


The Liquid Crystal Display consumes a very small amount of power and there is a type that only consumes power when changes are made (see Kent below). 

Kent Displays - Zero Power LCD display

Memory Chips & Programmers


MCUmall GQ-4X Programmer
MCUmall GQ-4X programmer supports  EPROM, EEPRO/Flash, Serial EPROM, MCU, SRAM, GAL/CPLD devices.  Purchased to read EEPROMs in old  Trimble GPS receiver and other equipment that use memory chips.

ICD2 PIC In Circuit Programmer

PicStart Plus DIP Programmer

UV Eraser

Byte Shop (Wiki)

On the East side of El Camino in Mountain view a small house was converted into a retail store selling home type computers.  It was called the Byte Shop.


HP came up with a way to calculate hyperbolic functions digitally to many decimal places of precision.  This was the first time that could be done and made books of tables obsolete.
3766370 Elementary floating point cordic function processor and shifter, J Walther, HP Inc, 1973-10-16, - "Three arithmetic units including three shifters are operated in parallel and controlled by a microprogram stored in a read-only memory to provide an improved elementary function floating-point processor. The microprogram includes a set of routines for calculating 20 elementary functions including arithmetic, exponential, hyperbolic, logarithmic, square root, and trigonometric functions. Each shifter is capable of reading a fixed plural number of consecutive bits, beginning with any bit position, from an associated data storage register."
Cordic Functions (Wiki).

3839630 Programmable calculator employing algebraic language, E Olander, R James, I Larson, R Watson, F Yockey, W Covington, J Walden, F Wenninger, H Russell, HP Inc, 1974-10-01, - HP 9810A
3859635 Programmable calculator, Robert E Watson, Jack M Walden, Charles W Near, HP Inc, 1975-01-07, - HP 9810A

HP 9100 (Wiki)

This was the first calculator that worked with things like logs, trig functions, unlike the prior calculators that only did add or subtract (and some could do multiply and divide or square root based on adding and/or subtracting).  The next generation was the HP 35 (Wiki) calculator.  It had the same computing power but would fit into a shirt pocket.

HP 9100
At Aertech in Mountain View, California we hand made tunnel diodes.  After the key electrical parameters were measured on each diode the cutoff frequency and another calculated parameters were needed.  The 9100 could do the calculations using a program that was loaded into the calculator.  Since it used core memory the program was always there.  We made a plywood top for a typewriter cart that had countersunk holes for the feet of the  9100 and there was a strap holding the 9100 to the cart.  This way we could wheel it to the test station where it was needed in a safe way.  This calculator was made before ICs were available.  It was about this time that a start up company called Fairchild, located in the same city, was offering RTL logic in round plastic packages that ran on 3.3 Volts.

The display was a CRT which showed  4 lines of the stack (as far as I can remember).  This made using reverse polish notation much easier for a beginner.
GB1197292 (eSpaceNet)  Calculator, Thomas E Osborne, HP, App: 1967-06-21, Pub: 1970-07-01, -

About this time the sports car magazines were carrying ads for the Curta Calculator (Wiki) that was a mechanical device that looked a lot like a pepper mill.  This was used for Time & Distance Rallies.

3176144 Selective signaling system, Robert O Gunderson, Edmund F Klein, NCR, 1965-03-30, - related to program control and core memory so may be related to the 9100?
YouTube: Interview with Dave Cochran about the HP 35 Calculator, 1:01:56 -

HP 35 (Wiki)

This was the first hand held calculator that would do scientific calculations and as an engineer working on microwave products, some of which were bound for the Vietnam conflict, I ordered an HP 35 with a DX-A2 priority, which meant HP had to ship my calculator prior to any shipped for civilian use.  This calculator does not have any programming ability, you can only use the canned functions.  The LED numeric display was a battery eater.
3855461 Calculator with key code association and display features, R Stockwell, HP Inc, App: 1973-08-30, Pub: 1974-12-17  -
3863060 General purpose calculator with capability for performing interdisciplinary business calculations, France Rode, Jr William L Crowley, Alexander D R Walker, David S Cochran, HP Inc,1975-01-28 - HP 35
3892958 Inverse/complementary function prefix key, Chung C Tung, HP Inc, 1975-07-01 -
4037092 Calculator having preprogrammed user-definable functions, Thomas E. Osborne, Richard Kent Stockwell, HP. App: 1973-11-26, Pub: 1977-07-19, - HP41?
4099246 Calculator having merged key codes, Thomas E. Osborne, Richard Kent Stockwell, HP, App: 1973-12-17, Pub: 1978-07-04, -  for example [Arc] [Sin]

HP 41 (Wiki)

The 41 uses an LCD alphanumeric display and can be programmed or can use plug in ROM modules.  Someone found a bug in the HP 41 that would allow getting into the native machine code.  This allowed writing code in machine language and the creation of the "Zen Rom" that has a huge number of new routines.  Printers, mag card readers and bar-code readers can also be plugged into the module slots.  The alpha aspect of the display make this a very powerful pocket computer.

HP 48GX (Wiki)

HP 48GX Calculator
This is a later version HP scientific calculator that also has an RS-232 port that I interfaced to a Motorola GPS receiver.  Has a graphic LCD display.

This is my everyday calculator, but early June 1023 the display shows '(Greek symbol for Pi)' instead of the number 3.1415......
Pressing Purple Shift Clear causes CLEAR to be displayed.  Pushing <- (left arrow) seven times erases it.
So far have not been able to get back to normal operation.  Let me know what's going on. Now fixed.

HP 80 Series Calculators

These were being sold during the time when the first models of the IBM PC were being sold.  The "C" in PC means computer and there were a number of government contractors that had strict rules about who could buy "computers".  By calling the 80 series machines "calculators" the purchasing process was greatly simplified.  These calculators have the ability to control instruments using the HP-IB interface allowing test automation.  Had a CRT display but I don't remember if it did graphics.

TI Speak & Spell (Wiki)

This was a very high technology item when first released in 1978.  Made use of Linear Predictive Coded Speech chips (Wiki).


Ver 1. Round orange and red keys (no yellow keys), Chliclet keyboard, Vacuum Florescent display, ,ti. logo in lower right
Ver 2. Membrane keyboard, Vacuum Florescent display
Ver 3. 2019 Membrane keyboard, no ext power jack, no headphone jack,  LCD display with narrow viewing angle, very small internal PCB.


Fig 1 Version 1, Round button Chiclet (Wiki) keyboard (Wiki).  <ti> logo in lower right corner.  No yellow keys only orange and red.  Extremely rare.
TI Speak &
Fig 2 Box.    
TI Speak &
Fig 3 Fun with Words! book.
TI Speak &
Fig 4
TI Speak &
Fig 5
TI Speak &
Fig 6   The daughter board is probably the power supply
 (Reddit: PSU) and includes a VFD output.
TI Speak &
Fig 7
TI Speak &
Fig 8 Each of the two keyboards supports a 4x5 array of keys, i.e. 20 keys.  Just like a TI hand held calculator.  So they used two calculator keyboards in the Speak & Spell.
TI Speak &
Fig 9 Power Supply
TI Speak &
Fig 10 after replacing 3 caps
Still not working.  Suspect active devices on
power supply board.
TI Speak &

Power Supply

First powered up using external power supply set to 6V and current limited to 1 Amp.  Grunge sound and bad ju-ju smoke smell.  This is very similar to the experience of Reddit user TheMightyMadman (Speak & Spell PSU).  But because I used an external HP power supply set to 6 Volts and with a current limit under 1 Amp the PCB was not turned to charcoal.

But my main board and the power supply daughter board (1033305-3, date code 8013) are older than than the Reddit main and daughter board (1033305-5, date code 8304).  I'm pretty sure this is the very first version.
The 8 connections to the daughter board shown are:
1. Speaker 1
2. Speaker 2
3. -3.5 Volts
4. -12 Volts
5. V battery (+6 V)
6. Ground
7. Start Up
8. Power Down


In cit
Removed Replacement

14mm x 5mm
4.7uf  50V
4.7 uF
4.7uf  50V
22 uF
22uF   25V

Fluke 87V Resistance shown in (). i.e. the 4.7uF Tant C2 was a dead short.
All three caps (C1, C2 & C3) appear to be bad.
Next remove and test stand alone and read C1 label.

Replacing C1, C2 & C3 did not fix it.  Suspect problem with Q1, Q2, Q3 and/or Q4.
Have 100 each SS8550 Silicon PNP transistors on order for under $10 including shipping.  (facing flat left to right: E, B, C).
There is a complementary NPN, the SS8050.


The Speak & Spell has 4 Rows x 10 Keys = 40 keys total.  Implemented as  two 4 x 5 (20) key matrix.  4 row wires + 5 column wires = 9 wires per group of 20 keys.
The white plastic for the group is marked (Fig 8) "Texas Instruments, Incorporated, Pat. Pend."
The white plastic also has 5 test points on a diagonal.

Miniature Electronic Calculator

TI handheld calculators (Wiki) with a 4x5 (20 buttons) keyboard layout: TI-1000, TI-1200, TI-1400, TI-1500, TI-1600 all probably use the same keyboard module.
3819921 minature electronic calculator, J Kilby (Wiki),  J Merryman (Wiki) Tassel James Van, TI, App: 1972-12-21, Pub: 1974-06-25, - the Prior art calculators cited in the patent were the desk top size, not hand held.  But HP had it's patent application in for the 9100 desktop calculator in 1967 and for the HP35 handheld scientific calculator in 1974.  The TI was the first handheld four function calculator.
Fig 1 has 8 digit display.
TI-1400 20
                  button, 4 function hand held calculator
Fig 2 Note the back of the 4x5 keyboard
has the same look and feel as the Speak & Spell Fig 8 above.
                            20 button, 4 function hand held calculator
Fig 3 It is the same 4x5 keyboard.
IC:  TMS0972NL
                            20 button, 4 function hand held calculator

Keyboard Patents

3684842 Pushbutton keyboard switch assembly with improved over center diaphragm contact, Henry J Boulanger, TI, App: 1970-07-01, Pub: 1972-08-15, -

3725907 Pushbutton keyboard system, H Boulanger, TI, App: 1971-06-01, Pub: 1973-04-03, - 4x5 Chicklet using staples as contacts

3767875 Diaphragm type pushbutton setting switch with fixed contact semiconductor substrate support, P Schneikart, R Murdock, J Day, TI, 1973-10-23, -

3783205 Keyboard switch matrix assembly with improved guide means for reducing transfer of bounding motion to movable conductor, H Boulanger, TI, App: 1971-10-27, Pub: 1974-01-01, -
3959611 Pushbutton keyboard system having
                    plural level wire-like contact, Herbert R. Greene,
                    Charles W. Balser, TI, App: 1975-01-10, Pub:
                    1976-05-25, - 4x5 Chicklet
3959611 Pushbutton keyboard system having plural level wire-like contact, Herbert R. Greene, Charles W. Balser, TI, App: 1975-01-10, Pub: 1976-05-25, -  4x5 Chicklet, improved staples are more reliable,

Fig 1: Note all wires come off one edge of keyboard assembly.

Fig 2. Note Chicklet keys with staples below metal dome as contacts.

Used in TI handheld calculators that have less than or equal to 20 buttons as well as Speak & Spell.


Computer on a Chip TMC0271-N2L (a TMS1000 (Wiki), Data_Manaul.pdf) variant); data code 8022;

Speech Synthesier TMC0281

TMC035INL (2ea) ROMs.

Converting speech into an electrical signal and converting an electrical back to speech is very important in the field of voice cryptography, machines.

Patent numbers on Speak & Spell (but related to calculators)

3921142 Electronic calculator chip having test input and output, John D Bryant, Glenn A Hartsell, TI, 1975-11-18, -

3934233 Read-only-memory for electronic calculator, Roger J. Fisher, Gerald D. Rogers, TI, 1976-01-20, -

3955181 Self-refreshing random access memory cell, Joseph H. Raymond, Jr., TI, 1976-05-04, -

3987416 Electronic calculator with display and keyboard scanning signal generator in data memory, Jerry L. Vandierendonck, Roger J. Fisher, Glenn A. Hartsell, TI, 1976-10-19, -

3988604 Electronic calculator or digital processor chip having multiple function arithmetic unit output, Joseph H. Raymond, Jr., Individual, 1976-10-26, -

3989939 Electronic calculator or digital processor chip with combined functions for constant, keyboard and control bit, Joseph H. Raymond, Jr., Individual, 1976-11-02, -

3991305 Electronic calculator or digital processor chip with multiple code combinations of display and keyboard scan outputs, Edward R. Caudel, Joseph H. Raymond, Jr., individuals, 1976-11-09, -

4005293 Pushbutton keyboard switch assembly having individual concave-convex contacts integrally attached to conductor strips, Henry J. Boulanger, TI, 1977-01-25, - Phosphor bronze dome

4064554 Microcomputer with code conversion, Graham S. Tubbs, TI, 1977-12-20, - to save memory space

4073006 Digital processor system with simultaneous branch and OP code function, Graham S. Tubbs, TI, 1978-02-07, -
4074355 Digital microprocessor system with shared decode, Graham S. Tubbs, TI, 1978-02-14, -

Speak & Spell and Related Patents

4188626 Method for scanning a keyboard and for actuating a display device via common conductors, Gene A. Frantz, George L. Brantingham, TI, 1980-02-12, -

4209844 Lattice filter for waveform or speech synthesis circuits using digital logic, George L. Brantingham, Richard H. Wiggins, Jr., TI, 1980-06-24, -

4295181 Module for an integrated circuit system, Richard R. Chang, Gene A. Frantz, William R. Hawkins, TI, 1981-10-13, - ROM module

4310831 Pulse width modulated, push/pull digital to analog converter, Alva E. Henderson, Gene A. Frantz, TI, 1982-01-12. - 30 pages or figures -

4357489 Low voltage speech synthesis system with pulse width digital-to-analog converter, Alva E. Henderson, Gene A. Frantz, TI, 1982-11-02, - Speak&Spell - 30 pages or figures -

4398059 Speech producing system, Kun-Shan Lin, Kathleen M. Goudie, Gene A. Frantz, TI, 1983-08-09, - uses 127 Allophones (Wiki) in a Linear Predictive Coding scheme.

4380371 Liquid crystal display device, Gene A. Frantz, TI, 1983-04-19, - not Vacuum Fluorescent Display?

4403965 Electronic teaching apparatus, William R. Hawkins, TI, 1983-09-13, -  Touch and Tell

4507750 Electronic apparatus from a host language, Gene A. Frantz, Kun-Shan Lin, TI, 1985-03-26, - Speech to Text
4516260 Electronic learning aid or game having synthesized speech, Paul S. Breedlove, James H. Moore, TI, 1985-05-07, -

4624012 Method and apparatus for converting voice characteristics of synthesized speech, Kun-Shan Lin, Alva E. Henderson, Gene A. Frantz, TI, 1986-11-18, - adds age and sex to speaker's voice.

4631748 Electronic handheld translator having miniature electronic speech synthesis chip, Paul S. Breedlove, James H. Moore, George L. Brantingham, Richard H. Wiggins, Jr., TI, 1986-12-23, - Touch and Tell

4685135 Text-to-speech synthesis system, Kun-Shan Lin, Kathleen M. Goudie, Gene A. Frantz, TI, 1987-08-04, - 39 pages of rules for LPC

4731847 Electronic apparatus for simulating singing of song, Gilbert A. Lybrook, Kun-Shan Lin, Gene A. Frantz, TI, 1988-03-15, - one version box has 12 note keyboard - adds pitch to speach

4749353 Talking electronic learning aid for improvement of spelling with operator-controlled word list, Paul S. Breedlove, TI, 1988-06-07, - 

4970659 Learning aid or game having miniature electronic speech synthesis chip, Paul S. Breedlove, James H. Moore, George L. Brantingham, Richard H. Wiggins, Jr., TI, App: 1978-04-28, Pub: 1990-11-13, -

7006995 Secure distribution of digital data, Roy I. Edenson, Peter F. van KesselGregory J. Hewlett, Paul S. Breedlove, William B. Werner, Keith H. Elliott, TI, 2006-02-28, - TIRIS Registration and Identification System for optical disks (copyright protection).

Vintage Computing and Gaming: 30 Years Later, Richard Wiggins Talks Speak & Spell Development -

Paul Breedlove: Originated the idea of a learning aid for spelling.
Gene Frantz: Responsible for the overall product design; spelling words, case design, display, and operation.
Larry Brantingham: IC designer.
Richard Wiggins: Voice processing algorithms.

Retroist: A History of the Speak & Spell;
Circuit Bending Wiki: Speak & Spell -
TI Voice Synthesis System manual (S%26S_IC_datasheet.pdf)
Reddit: Speak & Spell PSU
YouTube: Speak & Spell, Then & Now, 26:02 - 1033305-3 power supply

Federal Screw Works Votrax (Wiki)

This was a phoneme-based speech synthesizer IC used in arcade games, amateur radio stuff & much more. SC-01 was the first one.
Herb Caen, writing in the San Francisco Chronicle (Wiki), would mention the sign for Bay City Screw & Bolt (Wiki) and this company name reminds me of it.
3836717 Speech synthesizer responsive to a digital command input, R Gagnon, Scitronix Corp, 1974-09-17, -  - 32 phonemes

3908085 Voice synthesizer, Richard T Gagnon, Individual, 1975-09-23, - 64 phonemes

4128737 Voice synthesizer, Mark V. Dorais, Federal Screw Works, 1978-12-05, - - 128 phonemes

4130730 Voice synthesizer, Carl L. Ostrowski, Federal Screw Works, 1978-12-19, - 64 phonemes

4264783 Digital speech synthesizer having an analog delay line vocal tract, Richard T Gagnon, Federal Screw Works, 1981-04-28, - 64 phonemes

4301328 Voice synthesizer, Mark V. Dorais, Federal Screw Works, 1981-11-17,  - 128 phonemes

4433210 Integrated circuit phoneme-based speech synthesizer, Carl L. Ostrowski, Bertram White, Federal Screw Works, 1984-02-21, - 64 phonemes

4470150 Voice synthesizer with automatic pitch and speech rate modulation, Carl L. Ostrowski, Federal Screw Works, 1984-09-04, - 64 phonemes

4532495 Speech digitization system, Richard T. Gagnon, VOTRAX, 1985-07-30, - speech encoding system - AD7520 12 bit D/A converter, 

4829573 Speech synthesizer, Richard T. Gagnon, Duane W. Houck, VOTRAX, - 64 phonemes

HP & Agilent Rocky Mountain Basic Workstations

These came long before the PC and were typically used to control instruments using HP-IB, although some Computer Aided Drafting (Wiki: CAD) packages were written for them as well as other scientific uses.  Based on the Motorola 68000 series uP.  HP used their RMB workstations with their own CAD software to design HP products.

Magnetic Storage

When working in the 1970 we could buy direct from the government surplus equipment.  One of the things offered was a drum memory.  Never did get it, but it's a very early example of magnetic data storage.
2862199 Magnetic drum storage system, John E Scott, Sperry Rand, 1958-11-25, -
Later while at HP/Agilent I worked on the Hard Disk Spin Stand used to test heads and media.  I used air bearings.  But there was a design flaw, i.e. you can not use 50 Ohm coax cables to drive a write head.  They are OK for the read head.

Curta Calculator (Wiki)

YouTube: AT&T Tech Channel: Tech Icons: Cliff Stoll - The Curta Calculator, 9:42 -

DE747073C/en Calculating machine with a single
                  staggered roller surrounded by setting wheels,
                  Herzstark Curt, App: 1938-08-19, W.W>II, Pub:
DE747073C/en Calculating machine with a single
                  staggered roller surrounded by setting wheels,
                  Herzstark Curt, App: 1938-08-19, W.W>II, Pub:
                  1944-09-06 DE747073C/en Calculating machine with a single staggered roller surrounded by setting wheels, Herzstark Curt, App: 1938-08-19, W.W>II, Pub: 1944-09-06, -

DE747074C/en Calculating machine with only one
                  staggered roller, Herzstark Curt, App: 1939-04-13,
                  W.W.II, Pub: 1944-09-06
DE747074C/en Calculating machine with only one staggered roller, Herzstark Curt, App: 1939-04-13, W.W.II, Pub: 1944-09-06, -

CH266406A/en Adding machine, Herzstark Curt, 1950-01-31, -

2533372 Zeroizing Mechanism, C. Herzstark, Contina, 1950-12-12, -
RE23553 Zeroizing Mechanism, C. Herzstark, Contina, 1950-09-30, -
Same as DE873000C/en
2588835 Independent Actuator Tens-transfer
                  Mechanism, C. Herzstark, Contina, 1952-03-11
DE860420C/en Ten switching device, Herzstark
                  Curt, Contina Ag, 1952-12-22
2588835 Independent Actuator Tens-transfer Mechanism, C. Herzstark, Contina, 1952-03-11 -

DE860420C/en Ten switching device, Herzstark Curt, Contina Ag, 1952-12-22, -  uses Fig instead of Abb so there's a US version of this patent.  Found it.

DE872999C/en Small format calculating machine,
                  Herzstark Curt, Contina Ag, 1953-04-09
DE872999C/en Small format calculating machine, Herzstark Curt, Contina Ag, 1953-04-09, -Type 2

DE873000C/en Counter clearer for calculating
                  machines, especially miniature calculating machines,
                  Herzstark Curt, Contina Ag, 1953-04-09
DE873000C/en Counter clearer for calculating machines, especially miniature calculating machines, Herzstark Curt, Contina Ag, 1953-04-09, - Type 2


1950 Curta Calculator, 4:48 - Model 1,  some example computations
How the CURTA Works, 13:10 -

Web Pages - Type and Age of your Curta -


Delay Lines (Wiki) date to the 1920s (Wiki).  Mercury delay lines were developed for RADAR in W.W. II (Wiki)
2629827 Memory system, Jr John Presper Eckert, John W Mauchly, Eckert Mauchly Comp Corp, Oct 31, 1947 - digital data in Mercury

Magnetic Drum Memory dates to 1932 (Wiki).

2611813 Magnetic data storage system (disk drive), Jr Edwin S Eichert, Thomas K Sharpless, Technitrol Engineering Company, May 26, 1948, 360/49, 192/84.1, 360/72.1, 360/98.1 - first disk drive patent?


Computer Time Line - 3000 BC to 1998
Great Microprocessors of the Past and Present
Microprocessor instruction set cards
Chronology of Personal Computers

US Patent 3387286 Field Effect Transistor Memory, R. H. Dennard assigned to IBM, June 4, 1968 Classes 365/222; 257/296; 257/390; 257/E27.034; 257/E27.085; 365/149; 365/150; 365/182; 438/239; 438/275
Early computing at Morgan Crucible Co - 80 column punched cards and a drum memory controlled by tubes.
Ford Instrument Computer Mark 1 at the Analog Computer Museum and History Center
Michael Holley's SWTPC 6800/6809 documentation collection. -

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