Caption:

The earliest demonstrations of a practical electric telegraph were given in Britain in 1837. The following year William Fothergill Cooke developed a system for communicating between railway stations, using both four-needle and double-needle instruments. This double-needle telegraph was intended to be carried in trains and used in emergencies, when it would be brought out to the lineside and plugged into a junction box. It is not thought that the idea saw much use at that time, but the double-needle arrangement and the method of coding became the standard British system for over twenty years.