Communication leash
In the early days of the railroad, the communication line , also called the pull line or Harrison line after its inventor , was used by the passengers and staff of a train to alert the locomotive crew to a danger in the train and to ask them to stop.
The line ran from the end of the train through all of the cars and ended at a bell attached to the tender . The bell was later dispensed with and instead the line extended to the locomotive and connected to the whistle. Originally, the line ran on the outside of the train, above the windows, and was therefore difficult to reach for travelers. Moving it inwards should improve this. Basically, the problem remained that the line had to be carefully tensioned in order to actually trigger the signal when pulling, on the other hand, the tension must not be too great, for example when cornering or when the train starts due to the movement of the car the signal was triggered by itself. A possible break in the line was also dangerous, as a result of which a signal could no longer be given.
After a serious train accident near Shipton in 1874, the use of the pull line was only permitted to a limited extent. With the spread of the vacuum and compressed air brakes , which could also be operated by travelers using the emergency brake handles, the pull cord became increasingly superfluous and in Great Britain completely abolished in 1898. In Germany, too, the communication cord disappeared with the introduction of the continuous brake from the railway trains.