Reversing telegraph key used for the transmission of signals in the electric telegraph system.
This type of key was used in conjunction with long submarine telegraph cables which distorted electrical signals so that the normal on-off pulses used in land telegraphy to mark the dots and dashes of Morse code would not work. Instead, the direction of flow of signal current was changed so that current flowing in one direction signalled a dot and in the other direction a dash. The reversing key used two separate keys, one for each direction of current flow.
At the receiving end the sequence of current pulses were displayed as a wavy line on a moving paper tape which could be interpreted by the operator .
Manufactured in Melbourne by E. A. Machin & Co. sometime in the period 1907-1915. Similar to keys made by Elliott Bros., London.
Reversing telegraph key, with two brass contact spring blades with ebonite knobs. Mounted on a wooden base. Brass screw terminals.
E. A. Machin & Co., 377 Elizabeth Street, Melbourne, Greater Melbourne, Victoria, Australia, circa 1910
Sands & McDougall's Melbourne Directories list Machin, Ernest A. & Co., scientific instrument makers, at 377 Elizabeth Street, Melbourne for the years 1907-1915. From 1916, the address changed to 413-415 Elizabeth Street. Thus seems likely that this object was manufactured in Melbourne by E.A. Machin & Co during the period 1907-1915.
Base engraved: "E.A. MACHIN & CO. MAKERS 377 ELIZABETH STREET"
Type of item
125 mm (Length), 101 mm (Width), 54 mm (Height)
[Catalogue] 1895. Elliott Brothers (London) Catalogue., E4, 1895, Page 86, item 809 Pages