A Host of GPO Double Current keys.

001......This superb condition and rare GPO Double Current (Non-Reversing) Key with Send/Receive switch, dates from about 1860. The serial number is GPO 6. Used for transmitting morse code over land lines in the 19th century.
  • Mike / M0DVO adds: "This type of key is a Double Current Key, but achieves the polarity change by swapping between two batteries which have commoned opposite poles".


    002...... This classic style GPO Double Current Key has the grand glass round top. Dated around 1906.
  • Dennis Goacher / G3LLZ informs that there are Mark 1, 2 & 3 keys. (Mk 1 from 1885). The mark one has a glazed top to the cover and Capstain terminals (later ones had cheese head terminals). The mark 2 has a solid brass cover and cheese head terminals, and the mark 3 has a solid cover and milled terminals. (This could vary enormously as parts were sourced during production or replaced during servicing). Keys for the military invariably had solid covers and were stamped somewhere with a broad arrow.

    Key Drawing. Above is a drawing showing the contacts and general layout of a typical Double Current key.


    003...... A GPO Double Current key dated 26.07.07.

    Note from Dennis Goacher / G3LLZ......"The wood used for these keys was mahogany, although teak and oak bases can also be found".


     
     
     

    Circuit Diagram. Here is a view of the setup of the typical circuit with both keys set to Recieve. Note the addition for each station of batteries, relay, galvanometer and a sounder.


    004...... A nice GPO key with the serial number GPO 5438.


     
     
     
     
     
     

    009. .....A key here with no serial number, Nickel Plated for use in the colonies, purchased in Singapore.


     
     
     
     
     
     

    010......A fine key made by H. White & Co. 1918.


     
     
     
     
     
     


     
     
     

    053.....This fine scarce GPO FHB-53 Key with Send/Receive switch, was - I believe - the successor to the big double current keys.The key itself was possibly made by Signalling Equipment Ltd. England, and designated the model: Type "F-17"


    "BK"