Because you have skipped quickly over the decade before WWII when there were great advances in designing digital circuits with vacuum tubes, mostly in the UK, which have lead directly to the electronic circuits used in the British Colossus and in the US Atanasoff-Berry computer, and then in ENIAC, I want to fill in the gap between your 2 sentences:
> The Eccles-Jordan trigger eventually led to digital counters. In 1939, ...
After the Eccles-Jordan trigger mentioned by you, the following important steps were:
1929-07: “Hot-Cathode Thyratrons. Part II”, Albert W. Hull, where the inventor of thyratrons (at General Electric) describes a bistable circuit made with a pair of thyratrons, the second such circuit after the Eccles-Jordan trigger.
1931-01: “Note on the use of a thyratron with a Geiger counter”, N. A. de Bruyne and H. C. Webster, where it is suggested that the pulses produced by the Geiger counters for detecting radiation in nuclear physics experiments can be counted with electronic counters using thyratrons, since the existing mechanical counters were too slow for counting such pulses.
1931-07-02: “The Use of Thyratrons for High Speed Automatic Counting of Physical Phenomena”, Charles Eryl Wynn-Williams, where the first electronic digital counter is described. This counter was made with thyratrons and it was a decimal counter. For each decimal digit, a ring counter with 10 thyratrons was used. So the ring counter is the second kind of digital electronic circuit, after the simple bistable.
1932-05-02: “A Thyratron Scale-of-Two Automatic Counter”, Charles Eryl Wynn-Williams, where the first binary counter is described. It was also made with thyratrons, but it was an improvement over the decimal counter with ring counters per digit, as it required much less thyratrons and it was also more reliable.
1937-10: “A Scale-of-Two High-Speed Counter Using Hard Vacuum Triodes”, W. B. Lewis, where the first binary counter with vacuum tubes was described. This was an improvement over the counters with thyratrons, being much faster. The article "Trigger Circuits" from 1939, linked in TFA, cites this paper for its binary counter.
1938-01: “A Thermionic Trigger”, Otto H. Schmitt, where the Schmitt trigger made with vacuum tubes was described. The Eccles-Jordan trigger (a.k.a. R-S bistable) and the Schmitt trigger are 2 fundamental kinds of bistable circuits (i.e. the 3 values needed at the input of a bistable circuit, set, reset and keep the current value, can be encoded either with 2 binary inputs, as in the Eccles-Jordan trigger, or with 1 ternary input, as in the Schmitt trigger). Schmitt was American, but he invented the Schmitt trigger while working in the UK, where before WWII most of the work related to electronic digital circuits was done, mainly for applications in nuclear physics research.
I want to add an explanation of the word "trigger" because nowadays few people are aware of its correct meaning.
The early authors made a clear distinction between "trigger" and "latch", but the reasons for this have been mostly forgotten today, when almost nobody designs latches and flip-flops, because these are provided as library components in all FPGA or custom ASIC designs.
The Eccles-Jordan trigger, i.e. a closed loop formed by 2 inverters, was a "trigger" because it had a permanently active positive-feedback loop. To make it switch states, one had to force one of the outputs of the inverters towards its opposite state. That was difficult in the beginning, because the output pulled in the opposite direction to the forcing signal, trying to prevent the change. But after some threshold the modified output value went through the other inverter and then back to the output and due to positive feedback it began to pull in the same direction as the forcing signal. This triggered a very fast transition of the state. After triggering the transition it did not matter any more what the external forced signal did, the transition continued by itself.
The consequence of this is that even if the external pulse that forced the transition had a very slow rising rate, the Eccles-Jordan trigger switched much faster than its input, so it deserved the name "trigger".
The same is true for the Schmitt trigger, which also has a permanently active positive feedback loop.
Instead of using an Eccles-Jordan trigger made of 2 inverters, one can use an RS latch made of 2 NAND gates or of 2 NOR gates.
The RS latch is logically equivalent with an Eccles-Jordan trigger, but its switching behavior is very different. When the inputs of an RS latch are either "Set" or "Reset", the logical gates break the feedback loop, so the RS latch behaves like a cascade of 2 inverters without feedback, which follow the input. When the "Set" or "Reset" inputs are removed, the positive feedback loop is restored, latching the current state and keeping it until another set or reset command. Because of this, the switching of an RS latch is not "triggered", its outputs follow the inputs, with only a small rising or falling edge acceleration that is caused by the amplification of the gate in its linear range, the same as for an isolated logic inverter.
The D latch behaves in the same way as an RS latch, because for one value of its clock input the positive feedback loop is broken, allowing the change of the state, while for the other value the positive feedback loop is restored, latching the state.
Among the modern flip-flops, most are composed of latches, but there exist some types that are made with triggers.
The static RAM memory cells, like in the cache memories of CPUs, are normally made of Eccles-Jordan triggers, because the 2 inverters are simpler than the 2 NAND or NOR gates required by an RS latch.
After the Eccles-Jordan trigger, as I have written above, the next electronic bistable circuit was made in 1929, with 2 thyratrons. While the thyratron circuit looks almost identical with an Eccles-Jordan trigger, it functions in a completely different way.
A thyratron has internal positive feedback, so it latches a logic state by itself. But it does not have convenient set and reset inputs. The circuit invented in 1929 is actually a ring counter with 2 thyratrons, equivalent with a ring counter made with 2 flip-flops.
A ring counter can be extended to any number of flip-flops greater than 2. A ring counter with N flip-flops will have N states.
The same is true for ring counters with thyratrons. While the original circuit had 2 thyratrons, for 2 states, by 1931 ring counters with 10 thyratrons, thus 10 states, were made and used as components for a decimal counter, as I have said above.
I think it would have been more likely to be some kind of mechanical analog computer full of gears and cams (which some planes and missiles did use for guidance). Probably needing more support from the ground.
Apollo did carry tubes also, in the radio transmitters.
During the time of the Apollo project, from 1964 to 1969, the fastest computer of the world was CDC 6600, which was made with discrete transistors (and which greatly annoyed IBM, because a much smaller company had been able to make computers faster than theirs; the main designers of CDC 6600 had been Jim Thornton and Seymour Cray, who later became well known for the Cray supercomputers).
Integrated circuits became ubiquitous only during the late sixties.
Over on Youtube the Usagi Electric channel has several videos about reviving old vacuum tube computers and one of the interesting aspects is that tube failures are much less of an issue than the germanium diodes. The tubes are large and dramatic, but they're heavily outnumbered by the diodes. It was such a problem that the company built specialized test equipment that could identify bad diodes on the cards.
Vacuum tubes don't have the longest "natural" lifespan, but you also have to remember that early manufacturing techniques mean a lot more "bad batch" variability.
When part performance is more unpredictable, ease of maintenance is a much bigger deal for everybody all across the price/quality range.
> I'm also curious, if the cathode was grounded to the machine frame, how dangerous was it to do work on those machines?
When ground means earth, then: The chassis isn't dangerous at all. Its potential relative to other nearby things that are also connected to earth is ~0v.
When that's used as a supply rail (like for the cathode), it still works fine. It's still tied to earth.
You don't want to put any of your dinguses betwixt that and the +150v plate rail, but... I mean. :)
If you repaired televisions in the 70s, most of the IBM 604 trigger circuit looks completely ordinary: a couple of triodes, plate resistors, grid bias, coupling capacitors, and voltages high enough that you kept one hand in your pocket. Shirriff's observation that the trigger can oscillate, latch wrong, or refuse to switch unless the voltages are just right is especially familiar. We used to call that "the set’s acting up"; computer people called it logic margins. The later diode-controlled version is revealing too. Engineers weren’t escaping analog electronics so much as steadily boxing it in until the analog behavior became somebody else's problem.
Early digital hardware makes a lot more sense if you approach it with a voltmeter instead of a truth table.
Author here. I've powered up another tube module from the IBM 604, so let me know if you have questions...
Thanks for another interesting article.
Because you have skipped quickly over the decade before WWII when there were great advances in designing digital circuits with vacuum tubes, mostly in the UK, which have lead directly to the electronic circuits used in the British Colossus and in the US Atanasoff-Berry computer, and then in ENIAC, I want to fill in the gap between your 2 sentences:
> The Eccles-Jordan trigger eventually led to digital counters. In 1939, ...
After the Eccles-Jordan trigger mentioned by you, the following important steps were:
1929-07: “Hot-Cathode Thyratrons. Part II”, Albert W. Hull, where the inventor of thyratrons (at General Electric) describes a bistable circuit made with a pair of thyratrons, the second such circuit after the Eccles-Jordan trigger.
1931-01: “Note on the use of a thyratron with a Geiger counter”, N. A. de Bruyne and H. C. Webster, where it is suggested that the pulses produced by the Geiger counters for detecting radiation in nuclear physics experiments can be counted with electronic counters using thyratrons, since the existing mechanical counters were too slow for counting such pulses.
1931-07-02: “The Use of Thyratrons for High Speed Automatic Counting of Physical Phenomena”, Charles Eryl Wynn-Williams, where the first electronic digital counter is described. This counter was made with thyratrons and it was a decimal counter. For each decimal digit, a ring counter with 10 thyratrons was used. So the ring counter is the second kind of digital electronic circuit, after the simple bistable.
1932-05-02: “A Thyratron Scale-of-Two Automatic Counter”, Charles Eryl Wynn-Williams, where the first binary counter is described. It was also made with thyratrons, but it was an improvement over the decimal counter with ring counters per digit, as it required much less thyratrons and it was also more reliable.
1937-10: “A Scale-of-Two High-Speed Counter Using Hard Vacuum Triodes”, W. B. Lewis, where the first binary counter with vacuum tubes was described. This was an improvement over the counters with thyratrons, being much faster. The article "Trigger Circuits" from 1939, linked in TFA, cites this paper for its binary counter.
1938-01: “A Thermionic Trigger”, Otto H. Schmitt, where the Schmitt trigger made with vacuum tubes was described. The Eccles-Jordan trigger (a.k.a. R-S bistable) and the Schmitt trigger are 2 fundamental kinds of bistable circuits (i.e. the 3 values needed at the input of a bistable circuit, set, reset and keep the current value, can be encoded either with 2 binary inputs, as in the Eccles-Jordan trigger, or with 1 ternary input, as in the Schmitt trigger). Schmitt was American, but he invented the Schmitt trigger while working in the UK, where before WWII most of the work related to electronic digital circuits was done, mainly for applications in nuclear physics research.
Thanks for filling in the details! I figured that I was already going into too much history in my article :-)
I want to add an explanation of the word "trigger" because nowadays few people are aware of its correct meaning.
The early authors made a clear distinction between "trigger" and "latch", but the reasons for this have been mostly forgotten today, when almost nobody designs latches and flip-flops, because these are provided as library components in all FPGA or custom ASIC designs.
The Eccles-Jordan trigger, i.e. a closed loop formed by 2 inverters, was a "trigger" because it had a permanently active positive-feedback loop. To make it switch states, one had to force one of the outputs of the inverters towards its opposite state. That was difficult in the beginning, because the output pulled in the opposite direction to the forcing signal, trying to prevent the change. But after some threshold the modified output value went through the other inverter and then back to the output and due to positive feedback it began to pull in the same direction as the forcing signal. This triggered a very fast transition of the state. After triggering the transition it did not matter any more what the external forced signal did, the transition continued by itself.
The consequence of this is that even if the external pulse that forced the transition had a very slow rising rate, the Eccles-Jordan trigger switched much faster than its input, so it deserved the name "trigger".
The same is true for the Schmitt trigger, which also has a permanently active positive feedback loop.
Instead of using an Eccles-Jordan trigger made of 2 inverters, one can use an RS latch made of 2 NAND gates or of 2 NOR gates.
The RS latch is logically equivalent with an Eccles-Jordan trigger, but its switching behavior is very different. When the inputs of an RS latch are either "Set" or "Reset", the logical gates break the feedback loop, so the RS latch behaves like a cascade of 2 inverters without feedback, which follow the input. When the "Set" or "Reset" inputs are removed, the positive feedback loop is restored, latching the current state and keeping it until another set or reset command. Because of this, the switching of an RS latch is not "triggered", its outputs follow the inputs, with only a small rising or falling edge acceleration that is caused by the amplification of the gate in its linear range, the same as for an isolated logic inverter.
The D latch behaves in the same way as an RS latch, because for one value of its clock input the positive feedback loop is broken, allowing the change of the state, while for the other value the positive feedback loop is restored, latching the state.
Among the modern flip-flops, most are composed of latches, but there exist some types that are made with triggers.
The static RAM memory cells, like in the cache memories of CPUs, are normally made of Eccles-Jordan triggers, because the 2 inverters are simpler than the 2 NAND or NOR gates required by an RS latch.
After the Eccles-Jordan trigger, as I have written above, the next electronic bistable circuit was made in 1929, with 2 thyratrons. While the thyratron circuit looks almost identical with an Eccles-Jordan trigger, it functions in a completely different way.
A thyratron has internal positive feedback, so it latches a logic state by itself. But it does not have convenient set and reset inputs. The circuit invented in 1929 is actually a ring counter with 2 thyratrons, equivalent with a ring counter made with 2 flip-flops.
A ring counter can be extended to any number of flip-flops greater than 2. A ring counter with N flip-flops will have N states.
The same is true for ring counters with thyratrons. While the original circuit had 2 thyratrons, for 2 states, by 1931 ring counters with 10 thyratrons, thus 10 states, were made and used as components for a decimal counter, as I have said above.
integrated circuits were only invented a couple years before the Apollo moon missions started in 1961
imagine an alternate timeline where that didn't happen, could moon landing have even happened with vacuum-tubes? highly unlikely
Not sure if you've seen this video about how the Apollo computers were made, but it's really fascinating.
https://www.youtube.com/watch?v=ndvmFlg1WmE
(They also anachronistically refer to women as girls which feels weird nowadays.)
I think it would have been more likely to be some kind of mechanical analog computer full of gears and cams (which some planes and missiles did use for guidance). Probably needing more support from the ground.
Apollo did carry tubes also, in the radio transmitters.
In between IC's and vacuum tubes, isn't there discrete transistor logic?
Yes.
During the time of the Apollo project, from 1964 to 1969, the fastest computer of the world was CDC 6600, which was made with discrete transistors (and which greatly annoyed IBM, because a much smaller company had been able to make computers faster than theirs; the main designers of CDC 6600 had been Jim Thornton and Seymour Cray, who later became well known for the Cray supercomputers).
Integrated circuits became ubiquitous only during the late sixties.
btw this is what IC chips looked like during Apollo
* https://en.wikipedia.org/wiki/Invention_of_the_integrated_ci...
This is how they looked after removing the top of their package, not how they looked inside the computer.
This is how the silicon die looked like, with the ten bonded gold wires that went to the pins of the package.
What was the failure rate of those vacuum tubes, that they had to be so quick & easy to replace?
I'm also curious, if the cathode was grounded to the machine frame, how dangerous was it to do work on those machines?
Over on Youtube the Usagi Electric channel has several videos about reviving old vacuum tube computers and one of the interesting aspects is that tube failures are much less of an issue than the germanium diodes. The tubes are large and dramatic, but they're heavily outnumbered by the diodes. It was such a problem that the company built specialized test equipment that could identify bad diodes on the cards.
Vacuum tubes don't have the longest "natural" lifespan, but you also have to remember that early manufacturing techniques mean a lot more "bad batch" variability.
When part performance is more unpredictable, ease of maintenance is a much bigger deal for everybody all across the price/quality range.
> I'm also curious, if the cathode was grounded to the machine frame, how dangerous was it to do work on those machines?
When ground means earth, then: The chassis isn't dangerous at all. Its potential relative to other nearby things that are also connected to earth is ~0v.
When that's used as a supply rail (like for the cathode), it still works fine. It's still tied to earth.
You don't want to put any of your dinguses betwixt that and the +150v plate rail, but... I mean. :)
If you repaired televisions in the 70s, most of the IBM 604 trigger circuit looks completely ordinary: a couple of triodes, plate resistors, grid bias, coupling capacitors, and voltages high enough that you kept one hand in your pocket. Shirriff's observation that the trigger can oscillate, latch wrong, or refuse to switch unless the voltages are just right is especially familiar. We used to call that "the set’s acting up"; computer people called it logic margins. The later diode-controlled version is revealing too. Engineers weren’t escaping analog electronics so much as steadily boxing it in until the analog behavior became somebody else's problem.
Early digital hardware makes a lot more sense if you approach it with a voltmeter instead of a truth table.