te
end, the staff is _handed_ to the driver.

To render this system as safe as possible, train staff tickets are of
the same colour and shape as the staff for the section to which they
apply, and are kept in a special box at the stations, the key being
attached to the staff and the lock so arranged that the key cannot be
withdrawn unless the box has been locked.

ELECTRIC TRAIN STAFF AND TABLET SYSTEMS.

These systems of working are developments of the last mentioned, by
which are secured greater safety and ease in working the line. On some
sections of single line circumstances often necessitate the running of
several trains in one direction without a return train. For such cases
the train staff ticket was introduced; but even on the best regulated
lines it is not always possible to secure that the staff shall be at the
station where it is required at the right time, and cases have arisen
where, no train being available at the station where the staff was, it
had to be taken to the other station by a man on foot, causing much
delay to traffic. The electric train staff and tablet systems overcome
this difficulty. Both work on much the same principle, and we will
therefore describe the former.

[Illustration: FIG. 101.--An electric train staff holder: S S, staffs
in the slot of the instrument. Leaning against the side of the cabin is
a staff showing the key K at the end for unlocking a siding points
between two stations. The engine driver cannot remove the staff until
the points have been locked again.]

At each end of a block section a train staff instrument (Fig. 101) is
provided. In the base of these instruments are a number of train staffs,
any one of which would be accepted by an engine-driver as permission to
travel over the single line. The instruments are electrically connected,
the mechanism securing that a staff can be withdrawn only by the
co-operation of the signalman at each end of the section; that, when
_all_ the staffs are in the instruments, a staff may be withdrawn at
_either_ end; that, when a staff has been withdrawn, another cannot be
obtained until the one out has been restored to one or other of the
instruments. The safety of such a system is obvious, as also the
assistance to the working by having a staff available for a train no
matter from which end it is to enter the section.

The mechanism of the instruments is quite simple. A double-poled
electro-magnet is energized by the depression o