Photos of Phones and Phonographs (occasionally)

Uniselector Clock – progress video

As I’m sure I’ve mentioned – I’m building an electromechanical clock using relays and uniselectors salvaged from scrapped bits of old telephone exchanges.  We’re in the planning stages of making a video for the DFR Telecoms group, so I’ve been practising my editing skills making a video of my progress so far.

In service, it will be run from a 30 seconds clock pulse, but during testing I’m running it from a 2 second clock pulse so that I don’t have to wait ages for it to do anything.

Working from left to right on the relay strip, we have:

  • PA operates to the incoming clock pulse
  • PB,PC interact to divide the clock pulse by two (to give a 1 minute pulse) and step on the MU uniselector (which is used to update the “units” element of the minutes display)
  • Every 10 minutes, an earth is supplied by MU to operate MO, MOA – which interact to provide a pulse which steps on the MT uniselector (which is used to update the “tens” element of the minutes display)
  • Every 60 minutes, an earth is supplied by MT to operate HO, HOA – which interact to provide a pulse which steps on the H uniselector (which is used to update the “hours” elements of the display)

The 4th uniselector on the end, will be used to drive the westminster chimes – but I’ve not finished the design that bit yet.

The display wiring loom is complete, although the display unit itself (seen on the left of the first shot in the video) hasn’t been wired yet.  I’ve been offered some wood for the case (thanks Peter!) although I haven’t quite got as far as drawing up the sketches for that yet.

2 Responses to “Uniselector Clock – progress video”

  1. Lewis McCann says:

    Sounds like an interesting project!
    As you sound as if you are ex-GPO trained Telephone engineer I am wondering if you can point me in the direction of the spec of some uniselectors? They are type 2203A 4/30ASEG66/1.
    Appreciate your help.
    Regards, Lewis, ex ATE & Plessey.

  2. Paul says:

    Hi Lewis,
    Thanks for the compliment, but I’m not ex-GPO (I’m not old enough) I’m not even ex-BT – I’m just an enthusiastic amateur mucking about with this stuff. You’ll get a more authoritative answer out of a mailing list like the THG: (paid membership, but a good bunch!) TCI: (free mailing list membership I think) or the strowger mailing list – The THG would be especially useful as they would probably be able to dig up adjustment info etc for you.

    That said, I’m pretty sure the 2203A was a Type 4 (miniature, pluggable) uniselector with 3 non-bridging wipers. They’re all a standard coil resistance (I can’t remember how much, and I’m not near enough to one to measure it) and the pinout is reasonably easy to buzz out if you need it. The rest of the model number you quoted suggests the example you’ve got was made by Siemens in 1966 (I think)

    What do you want to know?


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