DTL logic. I've finally seen some.

[duncanlowe]

As a youngster learning logic ICs, there were TTL and CMOS. I'd heard of DTL but never come across it.

Today I was working through some bits and pieces I'd been given some years ago, but had stayed in a drawer since I got them. Given the history, one of these I'd assumed was some kind of high voltage probe. However on examining the components it's fitted with a couple of DTL NAND gates (FCH191) and a couple of what seem to be very early LEDs. I reckon it's some kind of home made logic probe.

I've found a data sheet from Philips, and they even compare and contrast DTL vs TTL. But I can't see that DTL had anything going for it. Am I wrong, or does history tell us that it didn't?

[Ed_Dinning]

Hi Duncan, if you want to go a bit further back in early DTL logic try looking up NORBIT. These were a DIL IC in steroids and I think were hybrid construction.
A good method for making simple control systems in the late 60's

Ed

[gingpeakin]

I've got loads of DTL stuff - both Mullard FC/FJ stuff and Motorola 930/960 stuff. Mostly it seems just like TTL but without the totem pole output stage. Just a 6k pull-up.

Ging

[G6Tanuki]

I cut my logic-teeth on the RTL Fairchild "uL" series of chips - uL914 and uL923 - they were deeply-simple logic-gates but they had - for us analog-fiends - the big thing that the 'paired' transistors were made on the same silicon-slab and so shared the same die-series and thermal environment - making them great for use in things like balanced-modulators, limiter/clippers etc.

http://datasheets-microeduc.blogspot...ntegrated.html

The first DSB signal I ever generated - as a schoolboy - used one of these in its balanced-modulator.

[Nuvistor]

I think the chronology was
Diode resistor logic
Resistor Transistor logic
Transistor transistor Logic

[Cobaltblue]

Norbit module

Cheers

Mike T

[factory]

The early digital AVO uses DTL for the display section & trigger board, they seem to be reliable as I've had no problems with them despite a PSU fault outputting 8V instead of 6V.

David

[dsergeant]

Likewise cut my teeth on DTL in the 1970s working for Ferranti. Even built my first electronic keyer with it. Probably still got some chips in the component drawer.

[dazzlevision]

And what about these - in the pre-IC days, from Mullard Equipment Ltd (later renamed MEL).

[Keith956]

DTL was the precursor to TTL. When I was at Fairchild Semi in the late 70's they were still making it, for military users, and it was very profitable as virtually no-one else made it anymore.

As far as I recall it had good noise immunity, but was not very fast due to resistive pullups.

When Fairchild introduced their 74F series logic, the process didn't support multiemitter transistors so the input stage went back to diodes rather like DTL.

[Craig Sawyers]

The Apollo guidance computer used RTL throughout. Mainly three input NOR gates, two per package.

Program ROM was rope memory, and RAM was core store.

Craig

[TonyDuell]

My minicomputer CPUs are mostly TTL but I wouldn't be surprised if there's the odd DTL IC in some of them. HP used a strange family called 'CTL' (Current Transfer Logic) in the 2100A CPU, and I have one of those to be restored sometime.

However some of the peripererals I have, like the Trend paper tape readers, are full of DTL chips. And the Solartron DTU is a mixture of TTL and DTL I think.

I got some of those Norbit modules at a museum sale a couple of years ago. I've downloaded a databook but haven't even tried to test them yet. I remember a competitor to those, the 'Minilog' series from Elliot, but I've never used those either. I may still have a couple floating around, but I gave most of them, alas, to the Bletchley Park museum.

[ortek_service]

Originally Posted by Nuvistor

I think the chronology was
Diode resistor logic
Resistor Transistor logic
Transistor transistor Logic

Although the originally mentioned DTL - Diode Transistor Logic - should also be there between RTL & TTL

[radioman]

I've got some old plug-in cards marked 'Elliot Automation Accessories Ltd' with 'Minilog Type S9' modules on them, whatever these are..
They are encapsulated in white epoxy resin but a few aren't and I can see germanium transistors and resistors, so assume they're RTL.

Andy

[The Philpott]

My Dad handed me some TTL and DTL assemblies for donation to my Physics lab. in 1987. I was impressed at the time that Dr.Smith actually asked what DTL was, rather than pretend he already knew. I already had an answer as i wanted to know what i was carrying!
Dave

[Craig Sawyers]

The late and very great Jim Williams had a wall hanging of the circuit boards from a minuteman missile. I have no idea what the guidance unit actually used for logic gates.

https://www.eetimes.com/a-magic-carp...al-messenger/#

Craig

[Rileyman]

Seeing "Elliott Automation" mentioned has reminded me that I offered a load of mainly DTL - based sub-assemblies , built on those very useful Elliott DZCU and DZCK p.c.b.s , in the Parts Offered section, on March 17th.. Not even a hint of interest , and now EVERYONE's talking about DTL !

[Diabolical Artificer]

Seeing "Elliott Automation" mentioned has reminded me that I offered a load of mainly DTL - based sub-assemblies , built on those very useful Elliott DZCU and DZCK p.c.b.s , in the Parts Offered section, on March 17th.. Not even a hint of interest , and now EVERYONE's talking about DTL

It's one thing to chat about DTL another to have an application for said boards.

[peter_scott]

My old HP9100 desk top calculator has loads of logic but perhaps you'd call it DL rather than DTL.

Peter

[Craig Sawyers]

The HP transistor noise analyzer 4470B selects the measurement function and range set by the front panel switches using discrete resistor-diode logic, supplemented by transistor switches. The output of those, control reed relays on each of the signal boards.

There are three boards dedicated to the discrete component logic.

Late 60's design.

Craig