This desirable Morse Key was created for use servicing the long submarine (under the sea) cables such as the Transatlantic Cable and dates to the c1920s. While regular Morse Keys (also known as tappers) would send their code of dots and dashes down the line using a single current, the vast distances of these submarine cables meant special dual polarity tappers had to be created to ensure the messages arrived.
The left key would create the dots and pressing it made the associated voltage positive. The right key would create the dashes and made the voltage negative. Each key has a unique tone when tapped to help prevent the sender from making mistakes. When these signals reached the other end of the wire they would usually be printed out on a paper strip to be read but ultra-sensitive relays were also sometimes used.
Naturally submarine tappers are far scarcer than regular Morse keys and although unlabelled this example is offered in very good original condition. There are two tiny chips to the top of the right key only. This has not been tested.
Approximate dimensions: 10cm wide x 13cm deep x 6cm high
