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ID = 30911
Brand: Hermeyer, Robert; Berlin
Tube type:  Relay in glass (not Relay Triode) 
Identical to Stabrelais-St57

Base Wires
Description This is a mercury relays for switching. They are fast and, most important, have a very small on resistance. 
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Collection of



Forum contributions about this tube
Threads: 1 | Posts: 4
Hits: 2669     Replies: 3
Unknown 'Stabrelais' by Hermeyer
Emilio Ciardiello
  1 Hello to everybody,

I found in my old stuff a strange component on which I have no data and few ideas about its use. May be that someone have already seen this item and knows something about its purpose and its manufacturer, Robert Hermeyer, Berlin. The components is named 'Stabrelais ST 57, Ka 16.

It is a small glass ampoule filled of mercury as far as I can see. It has two wires entering from the bottom and two additional wires on the side of the capillary over the mercury reservoir. The two wires on the bottom look like entering in a small bead placed just under the mercury reservoir. The resistance between the two wires on the bottom is 30 ohms. As you can see from one picture, it is given as 'Stabrelais'. The body is about 30 mm high by 4 mm dia.

In the past I saw crystal ovens using a mercury switch, a kind of small thermometer, to control the temperature. But this looks like having a self contained heater near the mercury. May be a kind of current sensing trip relais, but I never saw something similar.

Thank you,



Roy Johnson

Dear Emilio,

As mentioned by e-mail, I believe that it is a variety of mercury-in-glass thermostat.  I can now confirm this.

The normal type relies on conduction between two separated points on the capillary tube corresponding to an upper limit or with a contact in the reservoir of an additional lower limit.

With the apparent addition of a heating element in the reservoir this can have two main applications.

a) As a "simmerstat" - similar to an electric hot plate where the control element is remote from the heating element - effectively an on/off oscillator weakly depending on ambient temperature OR if the device is IN the controlled environment -

b) The heating element acts as a simplified differential action to approximate a 3-term servo system. This improves the closeness of temperature control by preventing overshoot and "hunting", just a domestic central heating themoststs have a small heater.     This is what I believe you have - a special close-controlled thermostat.

It would be useful to know if this was associated with a crystal oven and therefore possibly applicable to the Museum.  The small size may indicate that this is so.

Best regards,


Dietmar Rudolph † 6.1.22
  3 Dear Roy, dear Emilio,

I know these items from a Wandel & Goltermann Level Measuring Set PSM-5 (10 KHz - 30 MHz). This set only uses such mercury relays for switching. They are fast and, most important, have a very small on resistance. This is essential in the signal path of a level measuring set, which gives the level precise to a fraction of a dB.

Best regards,

Ernst Erb

Dear Emilio
First thanks for clearing the matter to Roy and Dietmar-
I have set up this "tube" now after loading up the maker. Since many collectors find items similar to thermoic vacuum tubes we introduce also such items in our tube list.

Can you now load up that picture you showed us? I think it is well done like this - or in two parts to show also the printing on the packeage.

One puzzle less ;-)

the thread is now also "sticked" to the "tube".

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