el, and above these the strips of multiple jacks. The rearwardly
projecting pins from the stile strips are for the support of the
multiple jack strips, these pins supporting the strips horizontally by
suitable multiple clips at the ends of the jack strips; the jack strips
being fastened from the rear by means of nuts engaging the screw
threads on these pins. This method of supporting drops and jacks is one
that is equally adaptable for use in other forms of boards, such as the
simple magneto switchboard.

[Illustration: Fig. 343. Drop and Jack Mounting]

[Illustration: Fig. 344. Keyboard Wiring]

In Fig. 344 is shown a detail photograph of the key shelf wiring in one
of these Monarch magneto switchboards. In this the under side of the
keys is shown, the key shelf being raised on its hinge for that purpose.
The cable, containing all of the insulated wires leading to these keys,
enters the space under the key shelf at the extreme left and from the
rear. It then passes to the right of this space where a "knee" is
formed, after which the cable is securely strapped to the under side of
the key shelf. By this construction sufficient flexibility is provided
for in the cable to permit the raising and lowering of the key shelf,
the long reach of the cable between the "knee" and the point of entry at
the left serving as a torsion member, so that the raising of the shelf
will give the cable a slight twist rather than bend it at a sharp angle.

CHAPTER XXVI

THE COMMON-BATTERY MULTIPLE SWITCHBOARD

=Western Electric No. 1 Relay Board.= The common-battery multiple
switchboard differs from the simple or non-multiple common-battery
switchboard mainly in the provision of multiple jacks and in the added
features which are involved in the provision for a busy test. The
principles of signaling and of supplying current to the subscribers for
talking are the same as in the non-multiple common-battery board. For
purposes of illustrating the practical workings of the common-battery
multiple switchboard, we will take the standard form of the Western
Electric Company, choosing this only because it is the standard with
nearly all the Bell operating companies throughout the United States.

[Illustration: Fig. 345. Line Circuit Western Electric No. 1. Board]

_Line Circuit._ We will first consider the line circuit in simplified
form, as shown in Fig. 345. At the left in this figure the
common-battery circuit is shown at the subscri