The electrical telegraph is a telegraph that uses electric signals . In general the term electrical telegraph refers to a signalling system where an operator makes and breaks an electrical contact with a telegraph key which results in an audible signal at the other end produced by a telegraph sounder which is interpreted and transcribed by a human . This was a practical electrical telegraph system , and subsequently electrical telegraph came to refer to a signaling telegram - a system where an operator makes and breaks an electrical contact with a telegraph key , which results in an audible signal at the other end produced by a telegraph sounder , which is interpreted and transcribed by a human .