1920s Telegraph GPO Standard Type B relay


1 in stock


1920s Telegraph GPO Standard Type B relay

This is an extremely rare 1920s Telegraph GPO Standard Type B relay, and is usually only seen in telecommunications museums e.g. the museum of technology. 

The reference number on the relay is:-


G.P.O 10329

This particular telegraph relay is a work of great design and engineering, and is in excellent condition. Even if you aren’t a collector of early telegraph or communications equipment, you can’t failed to be impressed by the brass and wood design. It would look wonderful as a paperweight or a desk ornament. An interesting Gizmo or Gadget to talk about in the office or seen gracing the shelves of a museum.

Approximate Measurements:

  • Base Diameter: 13cm
  • Height: 14.5cm

What is it?

In telegraphic communication, sound is transmitted as current via cables. Voltages and current are kept low in the cables for safety’s sake. If the cables are very long, the power has to be amplified in order to operate effectively (receive a signal) at the local telegraph station. On reaching the local station, the high resistance relay connects with the main cable. This results in an electrical contact within the relay, which is then passed in the local circuit to a battery and ‘sounder’, which produces the familiar Morse code ‘dots’ and ‘dashes.’

The relay consist of vertically mounted electric coils, which are polarised by a magnet which fits around the coils. When the current passes through the relay, it can make two contacts (with either ‘S’ or ‘M’, depending on whether or not the polarity is reversed). Lifting the glass lid on the relay exposes the local contacts allowing adjustment to ‘S’ or ‘M’.

The letters on the wooden base:-

  • S: Space
  • M: Mark
  • T Tongue
  • D: Down
  • U: Up

For a more technical explanation of telegraph relays then please click on the following link to this excellent resource reference from Salford University

Additional information

Weight 2.2 kg


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