Does anyone know what this is/ or does?

[Kwoods15]

I have this piece of equiptment but I have no idea what it does. Can anyone help out with a bit of info?

Writing in it is:
Plessey electronics

T.D.M.S Type: 5 ABV . 14E. Ser no: 7108.

Many thanks

Kerry

[ms660]

A bit about it here ?:

http://www.albinarrate.com/index.php...age&id=35:tdms

Lawrence.

[Kwoods15]

Thanks although I'm still none the wiser LOL.

[RF Burn]

In the days before the internet and mobile phones, one of the only ways to send text messages was by using teleprinters (abbrev. TTY, by the way 'Teletype' is a brand name). The teleprinter was an amazing feat of mechanical engineering which looked something like an electric typewriter but weighed many times more. You would dial up the telephone number of the person (or in the case of organisations it would most likely be a fixed line) then when they picked up you would start typing your message which would then be typed out at the receiving end on their machine. For those of us that remember the football scores on the telly on a Saturday afternoon, the camera was often focused on the printout of a teleprinter where the print head would jump up and down as it bashed out the scores on a roll of paper.

This piece of equipment was used to test the telephone or fixed line for quality of transmission, in other words measure the distortion and line loss. If the loss or distortion is too high then the message could have missing letters, become garbled or simply not print out at all. A bit like listening to music through a very small tinny loudspeaker with the volume turned up, much of the quality is lost in distortion.

You could also send text messages using radio communications, companies, government departments and embassies would use them regularly, also radio amateurs made use of machines manufactured by Creed to 'text' each other.

In addition to sending text messages the teleprinter saw service when used as a terminal (Like the VDU/Keyboard we use today) to input or output data to the very early computers. Such devices as the Teletype ASR33 and KSR33 would be chuntering away, slowly printing out the results of a running program, reading a program into the computer from their inbuilt paper-tape readers (before floppy and hard disc drives) or punching out a program on their paper-tape writers.

For those of us that think that 1Mbps (1 million bits per second) is very slow for our internet connection, these things operated at no more than about 300 bits per second!

Heady days!

[Andrew Sinclair]

Hello,
You have a Telegraph Distortion Measuring Set (TDMS). They were usually used in pairs. The TDMS6 is a signal analyser and the TDMS5 is a signal generator.

The TDMS5 produces 5 bit signals for testing telegraph lines or teleprinters themselves. It will produce a steady 0 or 1 (called mark or space) a constant 5 bit character set up on the 5 toggle switches below the CRT, or a quick brown fox message from an encoded disk inside.
The baud rate can be set up on a rotary switch and dial. For a Creed teleprinter, this would usually be 50 bauds for telex or 45.45 bauds for amateur radio operation.

The bias facility is for deliberately introducing distortion to see how well the teleprinter copes with it. There would have been specifications for the teleprinter that would have specified the amount of bias that could be applied before the characters were corrupted. The CRT shows the amount of bias, as spot on a circular timebase.

The multipin socket on the front panel is to test and adjust polarised relays which were much used in telegraph systems.

Inside you will find rows of double triode valves and metal rectifier diodes which form counters and logic gates. A friend described these instruments as "Collossus in miniature" refereing to the code breaking machine at Bletchley. (Ironically where my teleprinters ended up!).

The internal construction is beautiful. (Worth taking a picture and posting here.)
The TDMS6 takes a signal in from say, a teleprinter or punch tape reader and displays the logic level transistions as dots on a spiral timebase.

I think these instruments were orignally made by ATE at Bridgnorth. This firm was bought by Plessey. There were later transistor based models.

Hope this explains things a little.

Andrew

[Craig Sawyers]

We used to keep garbled teleprinter messages that came into our company for the general hilarity value in the early 80's. I kept one:

"Whatever happens, the entire instrument must fit inside a qwak not penob"

Craig

[The Philpott]

(Craig just made me remember an old East Anglian Daily Times typo which indicated a man had been arrested 'for illegal possession of a fireman')

It's a fascinating TDMS machine, and presumably of no practical use apart from interest and educational purposes..! A bit sad, really.

[qazxsw123]

I used to use one when repairing telex channel cards, makes a nice clicking noise

[TonyDuell]

I have one, along with the excellent manual. It's an interesting piece of digital valve technology. The unit (as mentioned) generates 5-level (bit) teleprinter characters, these are internally in parallel (either from the row of 5 switches or from the 'coder' which I will say more about in a moment) and converted to serial using a ring counter made from triodes.

At the back are 2 plug-in cans with deliberately different polarising pins so you can't swap them round. One is a normal Carpenter (polarised) relay. The other is the coder. It contains a disk of PCB-like material with contacts to generate the 'Quick Brown Fox' test message, Spring contacts rest on the disk and read out the characters. The disk is stepped on by a solenoid and ratchet mechanism inside the can (the manual I have goes into some detail on this unit, including exploded diagrams).

Another oddity is the way of checking the master clock frequency (which determines the baud rate, of course). There is a neon lamp on the panel which is driven at the baud rate. You are supposed to view it through a stroboscopic tuning fork and adjust for zero beat.

I find it of use when setting up my Creed teleprinters. Not sure if that's 'practical use' though.

[The Philpott]

Tony if you're using it that has to be good, no argument there whatsoever.

So this is really quite historically significant as one of those little known missing links between the analogue and digital world then..? Not to mention linking the mechanical and electronic world.

[AC/HL]

There was RY recurring as well, if I remember correctly?

[Radio Wrangler]

Some radio amateurs, just for the hell of it still use restored mechanical teleprinters along with FSK transmission to send typed messages the hard (and noisy) way. Mostly using Creed model 7B machines, which send the 5-bit Murray code (A predecessor to the ASCII code your computer most likely uses to represent alphanumerics and punctuation a binary codes)

The TDMS can be used to check the speed and make various adjustments to a teleprinter. The spiral timebase is used to check that the boundaries between each bit in the symbol are correctly timed

There are still people who could use it.

David

[TonyDuell]

To comment on the last few posts :

You don't get the spiral timebase on the TDMS5 (you might on a TDMS6, I don't have one), you certainly got it on later instruments (using those new-fangled semiconductor things). You have a circular trace that brightens for each transition. You can use the TDMS5 to monitor signals, you can look for distortion (signal changes at slightly the wrong time) as the bright dots don't all appear together, but you won't know which bit is 'out'.

I don't think the TDMS5 does RY. I have a later Trend test generator that does (and which also does ASCII, rather more comprehensive distortion, etc but which doesn't monitor the signal at all), it uses a mixtue of DTL and TTL ics. But I digress.

The TDMS5 will also let you test/set up Carpenter relays for transit time, bias, contact bounce, etc.

If you are going to use this unit, you do need the manual. It's quite complex....

There have been several 5-level codes over the years, and ITA2, which is the one used by Creed 7's etc, is not strictly Murray or Baudot code. But the name has stuck.

As for 'doing things the hard way', isn't that what we do here? I suspect it is easier to listen to an MP3 player than to set up (correctly) a turntable and pickup for LP's, for example.

Finally, I sort-of collect odd test instruments. Some to use, some becuase they are a forgotten part of electronics.

[wireless_john]

Long time since I've seen one of those! In my time in the Royal Navy, every ship with teleprinters had one. I still have some 5 unit tapes which produce things like the Blackpool Tower, Madonna and Child, Mona Lisa and so on. Nothing that will read them now but it always seemed a shame to throw them away!

John

[lesmw0sec]

I got into trouble one night with an ASR33. If the device is not active for a while, the motor times out and it just sits there quietly.
I was slaving on some software at around 3 am on one occasion in the attic above the bedroom. Forgetting that the 33 was still on, I did a list/scroll on the work. The Teletype burst into life with the usual racket, causing my previously sleeping wife to leap out of bed. I was not popular!