Datel Modem 1979 to 1982, anyone used it?

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CMcDougall
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Datel Modem 1979 to 1982, anyone used it?

Post by CMcDougall » Sat Jul 07, 2018 12:43 pm

I saved this BT Datel Modem No 13B ((saved from a damp /flooded ex nuclear bunker!) data plug rusted to bits), chips are dated 1982 wk23 & phone 3rd November 1977, the only info I can find is one made by PO sold on eBay (£29) but No 13A dated 1979.

Other info is it was 300bits a second.
Any other info on this, did the Acorn Atom use it? or even a beeb?

Can supply better pictures when sun is back out!

http://www.computinghistory.org.uk/det/ ... -Type-13A/

4/5 down http://telephonesuk.co.uk/phones_1960-80.htm

eBay completed : https://www.ebay.co.uk/itm/Post-Office- ... 7675.l2557
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Re: Datel Modem 1979 to 1982, anyone used it?

Post by Coeus » Sun Jul 08, 2018 4:50 pm

I think I have seen one of those but never used one in person, though I do remember the days of 300, then 1200, then 2400 bps.

There may be two reason why it was integrated into a phone:

1. It probably wasn't auto dialing so the phone would be needed to dial the connection.
2. The post office was still nationalised and could be really strict about what could be connected to a phone line hence the reason for acoustic couplers. By being integrated into a PO approved telephone no doubt this could then be directly connected.

No idea if anyone has ever used one on an Acorn machine. Any idea what interface it has? RS232 is presumably the most likely. If so it should have been possibe, it is just a case of whether anyone actually did it.
Last edited by Coeus on Sun Jul 08, 2018 4:51 pm, edited 1 time in total.

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by CMcDougall » Mon Jul 09, 2018 10:10 pm

^yeah number2, don't plug TalkTalk, PlusNet & Sky rubbish in :lol:
seems PO /GPO had total control of the market pre1970, so must be why it was all their stuff plugged in Only.

here is the plug for it, I had to cut it off as the cable had turned to glue /string :(
if left another year, whole thing would be same :|
the pins are as follows : black20 white3 green2 red7 orange6 blue8
datel Plug to PC black20 white3 green2 red7 orange6 blue8.jpg
pins 1to25
so, the PO/GPO one was serial number 9832, so where is the other 9831 :shock:
& wonder where the other 19,012 BT ones have gone...

here is it's back plate after a good clean :
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plate
& it's guts cleaned :
100_7298.JPG
PCB
joined a few antique phone pages on FarceBook, only one guy Mr T. Hammonds came up with this info:
"I think this is a Bell 103-compatible 300 Baud modem. You would use the phone to dial into the modem on the other end, and the buttons on top of the phone handle the exclusion circuit (making sure the data call is not interrupted by picking up the handset).

I haven't used this specific one. But we had similar modems in the US, way back when. My experience was with a similar setup used by an IBM 4341 mainframe computer to connect to remote offices and to IBM for maintenance and diagnostics.

That was before PCs. This machine had tape drives and HUGE 40 MB disk packs that were about the size of a washing machine."
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Re: Datel Modem 1979 to 1982, anyone used it?

Post by 1024MAK » Mon Jul 09, 2018 10:30 pm

CMcDougall wrote:
Mon Jul 09, 2018 10:10 pm
^yeah number2, don't plug TalkTalk, PlusNet & Sky rubbish in :lol:
seems PO /GPO had total control of the market pre1970, so must be why it was all their stuff plugged in Only.
Unless you lived in Hull, or worked for a large company that had their own telecommunications / telephone system...

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by 1024MAK » Mon Jul 09, 2018 10:42 pm

CMcDougall wrote:
Mon Jul 09, 2018 10:10 pm
This machine had tape drives and HUGE 40 MB disk packs that were about the size of a washing machine."
When I was at school, they organised a trip to a Westland Helicopter factory. One of the rooms had two rows of eight (I think) hard disk drives the size of washing machines. This would have been in the mid-1980's. Westland's used computers for stock control. So every time a part moved through the factory, it was logged.

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by CMcDougall » Mon Jul 09, 2018 11:04 pm

^Helicopters, better than our outings, in mid80s our primary school only went to see the Edinburgh train station & the space /universe museum 8)
1024MAK wrote:
Mon Jul 09, 2018 10:30 pm
or worked for a large company that had their own telecommunications / telephone system...
yeah, older large hospitals have their own 'exchange', seen them in the cellars as well. Handy for phoning Ghostbusters :lol:

wish I kept my springy PO Buzby from 1978, the sping got all tangled up, so went in bin :(
still got the badge though :D
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Re: Datel Modem 1979 to 1982, anyone used it?

Post by Commie_User » Mon Jul 09, 2018 11:16 pm

Is there any scope for you to use it, even between just two BBCs?

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by CMcDougall » Mon Jul 09, 2018 11:34 pm

^ not really, just wondered if anyone else has one / seen one.
seems this is ULTRA LOL RARE, as can't find anything on this one, just 2x GPO mkA ones in existance.

would not know where to start, someone has disconnected the wires in the phone to modem, & can't
find any info on it at all, or pics to follow to reconnect it all up.

inside phone part, the yellow taped 3wires are to exchange (again had to cut off),
& the grey tape is the the leads disconnected to convert just to phone (? or unused?) probably done 1984ish :
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Re: Datel Modem 1979 to 1982, anyone used it?

Post by 1024MAK » Tue Jul 10, 2018 12:24 pm

Commie_User wrote:
Mon Jul 09, 2018 11:16 pm
Is there any scope for you to use it, even between just two BBCs?
MODEMs designed only for exchange line use normally need something to simulate the exchange... (or your own Private Branch Exchange - PBX). Although it may be possible to modify some so they can work as a private wire type (MODEM - cable - MODEM with no other equipment required).

There were (and still are) MODEMs that are only private wire types (still used at my workplace). These were available as four wire or two wire types (meaning two telephone line 'pairs', or one telephone 'pair'). And there are some MODEMs that can be configured as to connect to an exchange or operate as a private wire type. The most advanced MODEM I got my hands on had a private wire connection for the primary data path and an exchange connection, so it could auto dial via an exchange if the primary private wire link failed.

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by Coeus » Tue Jul 10, 2018 3:42 pm

1024MAK wrote:
Tue Jul 10, 2018 12:24 pm
MODEMs designed only for exchange line use normally need something to simulate the exchange...
For an auto dialing modem this simulation would need to be more complete but without autodial I wonder if you could get away with connecting a pair of these back to back and just provide the DC 50V.

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by 1024MAK » Tue Jul 10, 2018 4:19 pm

Coeus wrote:
Tue Jul 10, 2018 3:42 pm
1024MAK wrote:
Tue Jul 10, 2018 12:24 pm
MODEMs designed only for exchange line use normally need something to simulate the exchange...
For an auto dialing modem this simulation would need to be more complete but without autodial I wonder if you could get away with connecting a pair of these back to back and just provide the DC 50V.
Assuming the MODEM needs to detect the line voltage, you need to supply a current limited 40 to 50V DC supply, complete with suitable inductors [*](acting as band stop filters) to prevent the ac signal from being 'shorted out' by the low impedance DC supply circuitry. Then couple the ac signal through to the line for the second MODEM and maybe an attenuator (see later). Of course, if the output level of the MODEM is high enough (not tried this, so don't know, but equipment designed/certified for use on the GPO/BT network has a defined maximum signal level) then it may be possible to just use resistors or an attenuator in place of the inductors.

[*] Some older exchange / concentrator / line set units used a special PO relay set to do this, the coils also acting as a current limiter.

If the MODEM does not detect the line voltage, it may be possible to just a resistor network to link the MODEMs (known in the telecommunications trade as an attenuator, an arrangement of resistors to limit the passed signal power, but still correctly matching the 600 ohm line impedance).

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by colonel32 » Tue Jul 10, 2018 5:51 pm

What are the differences between exchange modems and private line modems, in layman's terms? I've never known.

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by 1024MAK » Tue Jul 10, 2018 6:15 pm

The lines from an exchange have a current limited 50V supply. The MODEM (or telephone on the same line) has to 'load' the line (called going off-hook, same as when lifting the handset of a normal two part telephone, the line voltage then falling to between 3V and 12V approximately) then dial the number of the 'computer' that you wish to communicate with.

A private wire MODEM just connects to a voltage free telephone cable (in practice often a whole network of cables connected point to point).

In practice, both may use transmission systems if the route is long distance. But different transmission interface 'cards' are used.

Private wire MODEMs are normally only used by businesses, government and universities etc. to link between two fixed sites. So for example, the electrical distribution companies used to use them to link control and monitoring equipment at remote sub-stations to control centres.

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by vanpeebles » Wed Jul 11, 2018 6:57 am

If all the phones go off in a street in Scotland, we will know why :lol:

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by Coeus » Sun Jul 15, 2018 7:33 pm

I think I have just spotted one of these in use in Episode 10 "At The End of the Line" of "Making the Most of the Micro" at about 11:45. See this still:
Screenshot from 2018-07-15 20-14-36.png

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by CMcDougall » Sun Jul 15, 2018 9:26 pm

Good spot! :shock:
does look similar, but into a New Brain computer , thought they were only Forth language instead of Basic.
anyways, will watch the video linky when next on laptop (as my mobile can't cope :oops: )
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Re: Datel Modem 1979 to 1982, anyone used it?

Post by Coeus » Sun Jul 22, 2018 10:23 am

CMcDougall wrote:
Sun Jul 15, 2018 9:26 pm
Good spot! :shock:
does look similar, but into a New Brain computer , thought they were only Forth language instead of Basic.
anyways, will watch the video linky when next on laptop (as my mobile can't cope :oops: )
Well done for spotting that it was a New Brain. So this is the thing was supposed to be turning into the BBC Micro before the Acorn Proton did.

Interestingly, there are lots of BBC Micros in the BBC TV series but also plenty of other computers too. I think Commodore PETs and Apple IIs are the most common models but there are plenty I don't recognise.

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by Tweever » Sun Sep 09, 2018 9:09 pm

Hi, yes I've used one. It's nothing Acorn specific. It was a 200/300 bit/s V24 asynchronous outstation modem used to manually initiate calls to a computer bureau or similar. Examples include schools accessing external computer facilities using a slow-speed keyboard and printer / teletype. Another 1980's application example was retail chemists placing daily batch orders to their wholsalsers etc. The central site would have a bank of modems that would auto-answer the call to access the application / system. That's it really, it was a much smaller feature-stripped modem that did most of what the (larger) Datel 200 (Modem 2B) which was a much bigger and much more expensive box of slide in cards! If you are ever disposing of it pls let me know as I (rather sadly!) collect old uk telephones and it's a bit of an odd one! Cheers, David.

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Re: Datel Modem 1979 to 1982, anyone used it?

Post by CMcDougall » Sun Sep 09, 2018 9:40 pm

Tweever wrote:
Sun Sep 09, 2018 9:09 pm
Hi, yes I've used one
welcome David :)
thank you very much for the information on this! 8)
I have other old phones, even older than the one on top of this Data modem.
have had them from being a kid , ie 2years old :oops: , my dad changed it so could listen to music on it, and record my voice onto reel to reel tape :o
it did not work before, and I still can't get it to work, but could easily change to the 'newer' PCB version & it would work, but wanted to keep it original...
says on back of it "706L GNA 67/1" in white, with the letters on outside of the dial with 0-9 numbers on it .
my other not so old ones are "746 GNA 73/1" , "741 GNA 80/2" & "746F/SPK/75/1"
only difference no letters on dial, and a PCB inside, colours grey / green / etc.
pity are only worth about £20 each if lucky :cry:
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Re: Datel Modem 1979 to 1982, anyone used it?

Post by Tweever » Mon Sep 10, 2018 7:26 am

Hi slightly off Acorn topic but the 706 711 phones were earlier "700 series" the later cost reduced ones were 746, 741 etc. The GNA ones were made by Pye TMC at Airdrie and the other SPK one by Speke Telephones in Liverpool which may have been part of ATE (Plessey) group. Pls PM me if you need any other info.

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