Aquinas' definition. The Oxford Concise Dictionary of the Christian Church defines acedia (or accidie) as a state of restlessness and inability either to work or to pray. Some see it as the precursor to slothâone of the seven deadly sins.
A train horn is a powerful air horn that serves as an audible warning device on electric and Diesel locomotives. The horn's primary purpose is to alert persons and animals to an oncoming train, especially when approaching a grade crossing. The horn is also used for acknowledging signals given by railroad employees, such as during switching operations.
For the physical signals themselves, see railway signal. The freight train (right) is waiting at a red signal while the passenger train (left) crosses its path at a junction. Railway signalling is a system used to direct railway traffic and keep trains clear of each other at all times. Trains move on fixed rails, making them uniquely susceptible to collision.