tter battery is operated by hand and is
of a non-locking type. In some cases, where the operators are very busy,
a foot switch is used in place of this key. The use of such a key or
switch in practical operation has been found perfectly satisfactory, and
it takes the operators but a short time to become used to it.

The circuits of the dispatcher's office are similarly arranged, Fig.
495, being designed especially to facilitate their operation. In other
words, as the dispatcher is doing most of the work on the circuit, his
receiver is of a low-impedance type, which gives him slightly better
transmission than the waystations obtain. The key in his transmitter
circuit is of the locking type, so that he does not have to hold it in
while talking. This is for the reason that the dispatcher does most of
the talking on this circuit. Foot switches are also employed in some
cases by the dispatchers.

=Test Boards.= It is becoming quite a general practice among the
railroads to install more than one telephone circuit along their
rights-of-way. In many cases in addition to the train wire, a message
circuit is also equipped, and quite frequently a block wire also
operated by telephone, parallels these two. It is desirable on these
circuits to be able to make simple tests and also to be able to patch
one circuit with another in cases of emergency.

[Illustration: Fig. 496. Test Board]

Test boards have been designed for facilitating this work. These consist
of simple plug and jack boxes, the general appearance of which is shown
in Fig. 496. The circuit arrangement of one of these is shown in Fig.
497. Each wire comes into an individual jack as will be noted on one
side of the board, and passes through the inside contact of this jack,
out through a similar jack on the opposite side. The selector and
telephone set at an office are taken off these inside contacts through a
key, as shown. The outside contacts of this key are wired across two
pairs of cords. Now, assume the train wire comes in on jacks _1_ and
_3_, and the message wire on jacks _9_ and _11_. In case of an accident
to the train wire between two stations, it is desirable to patch this
connection with a message wire in order to keep the all-important train
wire working. The dispatcher instructs the operator at the last station
which he can obtain, to insert plugs _1_ and _2_ in jacks _1_ and _10_,
and plugs _3_ and _4_ in jacks _3_ and _12_, at the same time throwing
th