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ID = 81864
Tube type:  Relay in glass (not Relay Triode) 
Identical to HB-7020

Was used by Industrial

SPST mercury displacement contactor. In these devices an iron plunger floats on a mercury pool into a glass tube mounted inside a coil. When the excitation current flows into the coil, the plunger is attracted downwards so forcing the mercury to rise until it wets the contacts on the top of the bulb.

Due to the properties of mercury this kind of switch exhibits unique features which can be summarized in a very long and stable life, quite operation, extremely fast switching time, typically under 50 ps. Its operation is also safe against possibility of contact glued due to melting by overloads.

Unfortunately use of mercury contactors has been greatly reduced due to the problems that mercury creates for the environment when it is disposed of incorrectly.

  • SPST, 30 A at 110 VAC or 20 A at 220 VAC
  • 110 VAC 60 Hz coil
  • Fail-safe operation when coil is de-energized
Information source -- Collector info (Sammler)   Label on the device
- - Manufacturers Literature   1946 HB catalog
HB-7020: Private collection
Emilio Ciardiello

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