David Edward Hughes Second Model Printing Telegraph
The function and method of data transmission of Hughes telegraph instruments stayed basically the same. What changed were the implementation and the hardware. This model was UK patent #938, (1858) and USA patents 22531 & 22770 (1859).
A number of improvements were made; the helical scanning component was replaced by a rotating commutater. The horizontal vibrating timing spring was redesigned into a vertical vibrating rod and the instrument was made more robust. The keys were switched to a piano format.
This model was also used in tests with Cyrus Field on the Atlantic Telegraph Cable while it was in storage. To increase the instrument sensitivity, Hughes added a sensitive galvanometer type relay and pulse polarity changer to his receiver. He also slowed the speed of transmission down and lengthened the transmitting pulse to make it compatible with the retardation experienced with the undersea cables characteristics.
These additional features were covered in UK patent #1002, 1858.