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Linked to non-existing "Bell signals" page
The largest part of each token instrument is a 'magazine' consisting of four vertical channels, which stores each machine's stock of tokens. Because each token has a large head, wider than each channel, they can be moved around inside the magazine but not removed. Above the magazine is a lock mechanism called a 'commutator'. This is the only route by which tokens may be taken from or placed into the instrument, by turning the token like a key in a lock.
Alongside the commutator is a bell plunger used [[Bell signals|to signal to the other signalbox]], a telegraph needle which moves when the plunger in either instrument is pressed, and an indicator which reminds the signalman whether a token has been released or not. Some token instruments have automatic electrical indicators, but all of the instruments on the SVR have manual ones.
Tokens can be placed into an instrument at any time, if they fit, but a token can only be removed if all the tokens are in the two instruments, and the signalman at the other signalbox is holding down the bell plunger on his instrument.
== Operation ==
[[File: 1501_20120909.jpg|thumb|200px|right|As the train arrives, a token carrier is held out for the signalman to collect.]]
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.
Removing the token will unlock the signal which allows trains to enter the section of line between the two signalboxes. The signalman will clear this signal, put the token into a token carrier, and give it to the footplate crew, who will read the signal box names on the token out loud so all of the crew know they have the right token for their journey. As the train departs, the sending signalman will check it is showing the correct tail lamp at the end of the train, and send the "Train Entering Section" bell signal to the other signalman.