A Simple Morse Circuit

A single current Morse circuit
The earliest method for sending morse signals

1 - Sounder
2 - Relay
3 - Resistance Box acting as an artificial line.
4 - Single Current Morse Key

Single current Morse was the earliest method for sending morse signals. These are the components of a simple sounder circuit. Circuits of this type were in use on inland networks from the 1850s until the early years of the 20th century.

In this circuit diagram, the sensitive relay uses the weak current from the bottom (transmitting) circuit to switch on a larger battery in the top (receiving) circuit and so drive the sounder.

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