Curiosity – Old Set-Reset Relay - What, When, Where

[Mr.B]

My Uncle, a retired Electrical Engineer, was asked by a friend to help clean out some sheds from a deceased estate.
The sheds were absolutely full of tools, spare parts and junk.
During his journey he came across two of these relays and has kindly given me one.
It is clearly a set/reset relay.
However, it uses only one coil and an elaborate mechanical arrangement of springs, seesaws and a ball bearing.
One coil pulse sets, one pulse resets.
The base and cover are old brown Bakelite. It is unused as the cable entry breakouts are intact.
Marking on the back would indicate a coil voltage of 8V AC.

Questions:
1) Does anyone recognise the manufacturer printed on the back?
2) Does anyone know its approximate age?
3) Does anyone know in what applications such a relay may have been used?

Many thanks in advance.

More photos to come... Just have to wait for the one minute post restriction.

[Mr.B]

More photos…
More photos to come... Just have to wait for the one minute post restriction.

[Mr.B]

More photos…

[Towger]

I pulled a similar mercury switch from a very old washing machine, when I was a child.
It was so old it had a builtin mangle to help dry the clothes. Maybe 1930's ?


Edit: Add photo.

[slurry]

Second picture:
"Betriebspannung ~8V"
Thats in german, spannung=voltage and my best guess from the printing and look of it is that it's from the 40's
it does not look Siemens to me anyway.

[Towger]

You do know it contains mercury and not a ball bearing?

[Mr.B]

You do know it contains mercury and not a ball bearing?

It contains both by the way.

The mercury is in the switch envelope that closes the electrical contacts in the relay.
The ball bearing is in the rocker mechanism that controls the seesaw.
The ball bearing is absolutely integral to the control of the seesaw and is not easily seen in my photographs.





edit to add ball bearing clarity...

[Benta]

The "AZ" logo is Alois Zettler of Munich, Germany, nowadays Zettler Group. Since the 70s, there's a dependance in California, American Zettler, but I'd say this relay is older than that. And a US company would not print "Betriebsspannung" on a relay.
Operating voltage is 8 VAC, by the way.

[Mr.B]

The "AZ" logo is Alois Zettler of Munich...

Thank you Benta,
There isn't a lot around about Zettler Group, except their website.
This relay is clearly a lot older that the internet, however I was hopeful there would be something out there.

I am curious about what type of systems would have used 8vac as a control signal - it seems an unusual voltage.

[PA0PBZ]

The only thing I l know of that used 8V ac are old doorbells. I also remember the transformers having a 3-5-8V output.

[bktemp]

Yes, 8Vac was a common voltage for doorbells.
Its age is hard to tell, it could be anything from 40s to 70s.
It looks more expensive than the typical household device, at least I have never seen anything similar, but it does not like an industrial device.
Maybe the relay was used for switching stairway lighting in an apartment building using the doorbells voltage.

[SeanB]

Could definitely be that, use the low voltage to not have to run 2 way switches and intermediate switches for a series of lighting in a stairwell, so that any one of multiple parallel push button lights on each landing could be used to turn on the lights, and then you turn them off when you leave the stairwell. Better than leaving them on all night, or in a stairwell with infrequent use in a plant, but where you want light at demand.

Mercury relay has very high inrush capacity, because there is no erosion of the contact that wears it out, the vapour simply condenses back on the walls, and eventually runs back into the pool when it gets large enough drops formed.

[Twoflower]

You might be able to get more information if you look up the 'Pressmarke'. In the picture it's not clear visible but the top one could confirm "Alois Zettler GmbH, München" in case it's U3. The lower part it's not readable in the picture it tells you the material it is. But probably that doesn't help any further. Here you can get more information about it: http://www.radiomuseum.org/forum/pressmarken_praegezeichen.html#1 (sorry German).

Not sure how long Bakelite was used but probably it's older than 70s.

[Benta]

The application for this relay is common and also often used today (I have a couple of modern DIN-rail variants in my house).
It's for controlling the lights in hallways, stairwells, basements etc., where you need more switches than a simple multiway switch scheme can provide. Instead momentary switches are used to trigger a bistable relay like the one you have.
8 VAC was pretty much standard for apartment house doorbell systems and lends itself to this kind of lighting control as well. Today 24 VAC or 230 VAC control voltages prevail. I'm sure your relay was available in other voltages as well.

I'm sure that these relays are still present in the basement of thousands of older apartment houses in Central Europe today, although they are being replaced when upgrading the electrics.

[Neomys Sapiens]

Lighting control is a obvious application, as the mercury contact is not affected by the typical lamp switching. Whereas most appartment buildings have equvivalent relays with a timer function, it might have been used in a commercial building or maybe a hospital (they used the 8V AC too).

Keep your hands on it if you are into experimental and test applications: the mercury switch delivers a nearly instantaneous make and break wirh no chatter, very low resistance and is quite robust electrically!

[Mr.B]

Thank you all for your input.
The multi control point application in stairway lighting makes perfect sense.