First introduced for railway use in England between Euston and Camden in 1837, the electric telegraph permitted communication between fixed signal points. Each signalman was responsible for a portion of track known as a block section. Bell codes were used to describe the class and route of the train to be passed by the signalman to the next block section or to accept or reject a train from the preceding section. Generally, only one train was permitted in a section at one time; under poor visibility conditions a section was normally kept empty between every two trains. Many decisions of precedence were left to the individual signalman, and, with only limited information at their disposal, signalmen often made incorrect decisions, causing excessive delay.