A Host of GPO Double Current keys.

001......Courtesy of John Francis / G3LWI, this beautifully restored and very rare GPO Double Current Increment key dates from about 1860. The serial number is GPO 6. Used for transmitting morse code over land lines in the 19th century.


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.


     
     
     
     
     
     

    005. .....Serial number GPO 3470. 1908 (?)


     
     
     
     
     
     

    006......Serial number GPO 8915 in un-restored condition.
    Nickel plated brass fittingson the underside of this big key, plus lacquered brass fittings on the top with a nickel plated Send/Receive mechanism. During servicing at the various GPO factories parts were often replaced with whatever was at hand, so it is fairly common to see nickel and lacquered parts on these keys. Also - quite a few of these keys had all nickel plated parts on the underneath.


     
     
     
     
     
     

    007.......Serial number A150. Nickel Plated for use in the colonies. This key was used at CTO Cape Town.

    Info from Dennis / G3LLZ......"Early models had all the brass parts lacquered, but some later models were nickel plated and supplied for use in the colonies. Others were assembled with brass components above the ebonite base and tin plated, and later, nickel plated parts below the base".


     

    008......Serial number R31. Nickel Plated for use in the colonies. This key was used in South Africa.


     
     
     
     
     
     

    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.


     
     
     
     
     
     

    "BK"