ve already performed their functions and that,
therefore, are no longer needed. This switch may be seen best in Fig.
392 just above the upper bank of contacts. It is shown in Fig. 390
greatly distorted mechanically so as to better illustrate its electrical
functions.

[Illustration: Fig. 390. Circuits of First Selector]

The contact levers _1_, _2_, _3_, and _4_ of the side switch are carried
upon the arm _5_ which is pivoted at _6_. All of these contact levers,
therefore, move about _6_ as an axis. The side switch has three
positions and it is shown, in Fig. 390, in the first one of these. When
the private magnet armature is attracted and released once, the
escapement carried by it permits the spring _7_ to move the arm _5_ so
as to bring the wipers of the side switch into its second position; the
second pulling up and release of the private magnet armature will cause
the movement of the side switch wipers into the third position. It is to
be noted that the escapement which releases the side switch arm may be
moved either by the private or by the rotary magnet, since the armature
of the latter has a finger which engages the private magnet armature.

[Illustration: Fig. 391. Rear View of First Selector]

_Functions of Side Switch._ The functions of the side switch may be
briefly outlined in connection with the first selector, as an example.
In the first position it extends the control of the subscriber's signal
transmitter through the first selector trunk and line relays to the
vertical and private magnets so that these magnets will be responsive to
the selecting impulses corresponding to the first digit. In its second
position it brings about such a condition of affairs that the rotary
magnet will be brought into play and automatically move the wipers over
the bank contacts in search of an idle trunk. In its third position,
both the vertical and rotary relays are cut off and the line is cut
straight through to the second selector trunk, and only those parts of
the first selector apparatus are left in an operative state which have
to do with the private or guarding circuits and with the release.
Similar functions are performed by the side switch in connection with
the other selecting switches.

[Illustration: Fig. 392. Side View of Second Selector]

_Release Mechanism._ Another one of the features of the switch that
needs to be considered before a detailed understanding of its operation
may be had, is the mechanic