Communication was an important aspect of railway safety. This is a telgraphic instrument from the Channelsea Branch at Stratford.  Signalmen had to communicate to each other to  receive a train into their section, or to send it on to the next. Before the advent of the telephone a complex set of telgraphic codes had to be learned, so that this could be done efficiently. Each signal box had an identifying the number. (In the early days boxes were only perhaps a mile in either direction - or less on busy or complex routes). Each type of train also had an identifying code - from a humble goods, to a heavy passenger  express, and even the Royal Train, all  identified by a code of so many rings. This telegraph would ring when a message was sent to alert the signalman, offer him the train, or acknowledge receipt of a train into his section.  He would also be setting the route by altering points and signalling the train through the semaphore or colour-light signals. He also had to record train movements in his log book.