Changes

As an additional measure to deter a signalman trying to insert a token into the wrong instrument the differing tokens are colour coded either Red, Yellow, Blue or Green. This is colour is also carried on the knob on the top of the instrument

If signalman A wishing to send a train will send the "Call Attention" bell signal. When signalman B at the other end of the section acknowledges the "Call Attention" bell signal signalman A will send "Is the line clear for (the particular type of train)" ''n.b. there are different signals for different train types''. If the signalman B accepts the train they will respond by repeating the bell code but keep the bell plunger held in on the final beat of the signal. Keeping the plunger held in releases the mechanism of signalman A's token instrument, if no other token is presently withdrawn from either instrument, so the signalman can remove a token. When signalman A withdraws the token from the instrument both signalmen will set their indicators to show that a token is out, and in which direction the train is traveling.