MNDX 341

Update after 15 years maintenance!

Page being developed

First a view by the door showing how it should look. The battery box has been rebuilt and now contains the batteries. The spares cabinet has a new bridge shelf across to the table over the battery box. The spares cabinet is now the correct item and the fuse cabinet mounted in a more sensible place. A notice board finishes off the new look, and the small SCOT terminal still has pride of place plugged into a proper D socket mounted on the wall. Correct notices are also fixed up, and the steel bar for mounting the heater has been replaced.

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This shows the other front corner where a large PABX style rectifier has been used in place of the correct type 103 which was missing, but the correct switchboard has been mounted on top. On top of that is the Ceptel solid state announcer unit, CP/M based using 5 1/4 inch floppy disks. A standard GPO clock has been provided running from the local pulse clock supply.
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The MDF has been seriously tidied up after many roughly finished jumpers had been left by Teradyne. I have provided an EPG unit which would only be found in a main exchange under normal circumstances, but hopefully I am allowed a few extra embelishments?

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Before we leave this end of the trailer just another look back on the layout by the door. It is much more conventional than the mess that Teradyne had left it in with bits of the battery box etc having been carved up and used as shelves on the wall, no front on the First aid box etc etc.

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A general look down the centre isle of the equipment racks. Now fairly tidy and well equiped with relay sets and selectors.

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So now lets have a more detailed look at what we now have on the racks. Here is a peek behind the suite with the RSR, AER and Group racks. The blue boxes on the left are a bolt on extra from crossbar exchanges which are useful here to decode DTMF dialling into Strowger pulses. These are used for example, with incoming calls from the public network. The main exchange alarm lantern is another of my "not really correct" embelishments, but that having been said, one can never say that anything was never done like that or is out of place, because there are always exceptions! Note how narrow the working space is behind the racks, compared to a normal autofloor exchange. Its not so amusing after the first hour or two of wire wrapping (ask David)!



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Here is a view looking back towards the front. The call announcers and Divertacalls on the top left are an addition which are used with incoming calls for automatic answering of numbers to provide interest. The Announcers 12A were recovered from Toll B in London and still contain some interesting announcements, although the Eproms are starting to lose some data causing slight audio corruption in places. But they are probably at least 40 years old!

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And looking further down on the left we can see the test box has been resupplied, another item which Teradyne removed.

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This is the C&FC Linefinder shelf. Four unis had been stripped out with their associated LF and K relays from the relay set above. They are now replaced and all 10 linefinders work with the new C&FC 1st selector shelf, see later below.

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Another view of the C&FC linefinders and the new test case. Also now provided is a test number on 5299, the circuit for which is in one of the strip mount relay sets seen here. The magnetically mounted test box is used for testing meter pulses, full local call timing has now been implemented.


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You will never see a row of test selectors like this in many exchanges! Teradyne specialised in testing the routine test equipment they developed for use by BT and other telcom providers. SCOT and 4TEL were two examples of such equipment.

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And finally, the shelf shown here of 1st selectors, mounted on the RSR above the C&FC relays sets, was also a casualty of Teradyne's quest for spares, they chopped and took the whole shelf out! Fortunately I was able to locate an exact replacement for  the shelf but this did not overcome the enormous amount of work that had to be done to reconnect the hundreds of wires on the bank outlet at the back. I have just one payphone working in the K6 right now, but there are 4 more circuits ready for me to use when there are enough days in the week to do it all!


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Last but not least I would like to thank the following for their help and support over the last 15 years which made this recovery and renovation possible. In particular without the work and support of David I could not have coped with all the work involved on my own:

Teradyne who provided the MNDX
Ian Jolly who provided a suitable power unit swapping it over between trailers in the dead of the night at a Little Chef car park somewhere in Shropshire.
Nick Wellington who provided spare parts from recycled trailers
Steve Cashmoor who helped find spare parts at the bitter end of the Strowger era
David Williams who helped with everything else!



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