Vintage electrical device picture puzzle

[Lucien Nunes]

What's this out of? Brass cup about 2" diameter, porcelain ring inside, half filled with strange flaky powder with shiny specks of mica in it. There's another two of them in the unit. Over a century old.

 

[Deleted account]

Pass. Powder to absorb arching maybe. Some sort of dimmer device.

 

[tazz]

Knowing your trade, I`m going to take a guess at an early arc light or limelight base.

 

[Knobhead]

Is that a mica sheet it's stood on and is it a part of the setup?

 

[Lucien Nunes]

No it's standing on a steel surface-table in the engineering shop. But post #2 got it already. It's part of a dimmer, or more accurately 'Martin's regulator'. It works like a carbon pile or carbon granule mic, with three of these cups of powder in a stack. As you turn the screw it compresses contacts either side of the layer of powder, reducing its resistance. According to the 1907 patent, the powder contains carbon, mica and sand. As the pressure is relieved, the springy mica flakes separate the carbon granules so that the resistance varies smoothly.

This one looks like it was a salesman's sample or demo unit as it has a little ivorine label on the pattress showing its recommended applications. I tested it, the resistance variation isn't very smooth but I think some of the powder has been lost through it being taken apart in the past so it's not a fair test. I doubt many modern dimmers would work at all after 100 years though.

 

[R G]

The house I was working in last week may be of interest to you , it had all the old bell cranks and steel wires under the floorboards and pulls by the fire places , unfortunately the panel had been removed in the old scullery ...

 

[Lucien Nunes]

Yes one day we need to get a set of servants bell equipment for the 'non-electrical' comparison section. I have a variety of pushes, bells and a couple of annunciator boards, but not the mechanical variety to compare with.

I recently saw a very large annunciator with windows for more or less every room in the house, even the 'Maids Bath' had a bell push.

 

[R G]

If I can get back there I will speak to the owner and see if I can remove some of the bits for you , I used to see loads of bit years ago , lots in the West London area , I came across an old board that had a contactor setup with 2 mercury tube that hinged with contacts at each end and in the middle , with hindsight I wish I had kept it now ...

Some of the old enunciator panels were nice with a mechanical setup and a large battery to one side that rung the bell ,the flaps had a switch that made and the bell rung ...

 

[PEG]

Yes one day we need to get a set of servants bell equipment for the 'non-electrical' comparison section. I have a variety of pushes, bells and a couple of annunciator boards, but not the mechanical variety to compare with.

I recently saw a very large annunciator with windows for more or less every room in the house, even the 'Maids Bath' had a bell push.

Nice feature,Lucien,and a refreshing change from the shed RCD carry-on....

...As for the Maids' bell push,fairly standard round here,indeed,my three maids have one each...

Cheers :icon12:

 

[Lucien Nunes]

OK, so what if there's only one maid, and she's in the bath. She pushes her own button, what happens next? Who gets the ding-dong?