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I volunteer at the Dauphin Railway Museum in Manitoba, where we recently received a donation of equipment collected by CNCP Telecommunications in the 1970s and earlier.

Most has been identified, including testing equipment, telegraph relays, Telex terminals and a medical coil (!) but one piece has stumped everyone who's looked at it. It is a cylinder about 17cm diameter, wood at either end with a number of thick metal plates through it. On the upper surface there are a couple of connections for wire. The five hard metal posts on the top seem to be the heads of bolts to hold the whole thing together. A.E. Morrison (a former manufacturer of electric milk floats in the UK) is stamped into the top surface. I have not attempted to open it up as I suspect it would tell me nothing.

Top view

Underside

SamGibson
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Richard Simons
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  • @GregoryKornblum I'm not quite sure if your comment is productive or not, but it has certainly made my day! Richard, are these bolts isolated from the brass contacts? What do you see when you remove the brass curved plate? (the elongated screw holes in that brass plate definitely look like it was meant to be easily removed) – Marcus Müller Oct 07 '18 at 17:54
  • My guess: Spark gap of some kind. – Marcus Müller Oct 07 '18 at 17:54
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    The brass cover on the side is designed to be easily removed and put back on. What is behind it? – JRE Oct 07 '18 at 18:38
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    Less blurry, better pictures could help. As well as measuring continuity everywhere. Opening my tell you nothing, but someone else maybe more. Any moving parts? Not good for ee.se but a high Res video might work best – PlasmaHH Oct 07 '18 at 18:43
  • The bolts may help hold it together, but that is not their only job. The heads appear to be made to clamp wires onto. Also, there are five bolts and five metal disks. Too much of a coincidence. – JRE Oct 07 '18 at 19:13
  • An electric pencil sharpener? just looking at the hole in the plate :) I think Gregory may be correct though... – Solar Mike Oct 07 '18 at 19:26
  • Doubt it is a morse key. Might be some kind of electrical scribe for telegraph signals. – JRE Oct 07 '18 at 19:56
  • Has a look of a voice coil. What resistance is there between the two brass posts? – HandyHowie Oct 07 '18 at 20:11
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    it may be a part of a chart recorder for keeping a record of engine speed .... are the disks magnetic? – jsotola Oct 07 '18 at 20:33
  • @GregoryKornblum the morse key, not the buzzer... :) – Solar Mike Oct 07 '18 at 20:39
  • do any parts move? – jsotola Oct 07 '18 at 20:40
  • Could it be a gauge of some sort, perhaps to measure cylinder diameter? It appears a "feeler" went in the hole and it's extension was adjustable. – DrMoishe Pippik Oct 07 '18 at 22:35
  • can you remove the curved brass plate and take a couple of pictures of the inside? .... the metal bar that sticks out the bottom in the second picture appears to be composed of two metal strips separated by an insulator ....there may have been a wire stretched between the top and bottom contacts on that bar ..... maybe it is some type of a G-force sensor – jsotola Oct 08 '18 at 00:37
  • Thanks for the comments. I will try to respond to them in a couple of days when I next go in to the museum. – Richard Simons Oct 08 '18 at 16:08
  • Morrison also made Mercury Arc Rectifiers and Battery Chargers. That may be a solid state rectifier. – david Nov 16 '18 at 09:48
  • --also amplifiers, including early theatre sound systems. – david Nov 16 '18 at 09:56
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    I'm voting to close this question as off-topic because it has been abandoned by an asker who has not returned to the site since the day after posting, leaving clarification questions unanswered. – Chris Stratton Jan 04 '19 at 16:46
  • Sadly, I have to agree. I'd have rather found out what it is, but the question does appear to have been abandoned. – JRE Jan 04 '19 at 18:06

1 Answers1

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It is hard to tell the relationship of the circle cutout and the 2 adjustment screws, but Telegraph was popular and this looks like an arc suppression instrument that passes the high voltage used for telegraphy. Hence it has 2 screw adjustments for the centre conductor but it seems to me that it ought to arc near the inside of the circle cutout on the outer brass plate for a breakdown rating of about ~3kV/mm gap.

It would be something like a spark gap lightning arrestor used on powerline poles. The metal plates are added for mass and stabilizing the desktop unit. A.E. MORRISON and sons were prominent inventors and supplier of electrical equipment in the U.K.

Anecdotal

I remember as a kid for 4 years growing up on Kirby St, in Dauphin, Mb in the mid-'60s with my pickle jar radio and wire across the street, I could listen to Saskabush radio at night, get the "hummadidity" weather report when I should have been sleeping and listen to CKY in Winnipeg. My Dad never knew about the risk of an outdoor wire antenna to the tree across the street from stray lighting pickup on the antenna, but I wouldn't discover that till I did Seismic research for UofM during the summer of '73 on boat with 100m of cable going to an island... I loved my time in Dauphin with the schools, outdoor hockey, the Park Cafe and the Ukrainian Festival.

Regarding trains and the EMI radiated from the traction motors, it wasn't until 1982 I tested CATV coax lines one day in River Heights, Winnipeg that got interference from poor coax shielding from poor distributed earth-grounding that caused interference on the low band cable TV channels. MTS owned all the TV distribution cables and twisted pair phone lines at that time and we did Project IDA for them. Trains emit a lot of EMI up to 100MHz! at that time. This was a residential back lane that was 100m or so from the train tracks.

Tony Stewart EE75
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