Changes

== Operation ==

The signalman sending a train will alert the receiving signalman with the "Call Attention" [[Bell signals|bell signal]], and when he or she responds will, by bell signal, ask "Is the line clear for [this kind of train]", there being different signals for different train types. If the receiving signalman accepts the train, he or she will repeat the signal back, keeping the bell plunger held down on the final beat of the signal. Holding down the plunger releases the mechanism of the sending signalman's token instrument, so he or she can remove a token. When the signalman removes the token both signalmen will set their indicators to show that a token is out, and which direction it is travelling in.