Polarized Telegraph Relay

The relay is used to regenerate weak telegraph signals, for onward transmission. The terminals marked U and D with and without circles access the relay solenoids. The terminals marked T and M are the output contacts. The glazed lid with bevelled glass is removable to allow adjustments to the solenoid pole pieces. The key for this adjustment was under one of the terminals. There is an adjusting slot in the side of the brass casing to permit the adjustment of the contacts.
A polarized relay incorporated a permanent magnet in its design. Because this type of relay depended completely on magnetic effects, it was faster and more sensitive in operation than a non-polarized relay which incoporated a mechanical return spring.
Signed “Patent, Siemens Brothers, London”


Inventory Number: 



Diameter of base 14.5cm, overall height 10cm


Wooden base. Brass vertical cylindrical case with glass top. Brass terminals around base.


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