al relation of the holding and the release
dog. This dog is shown at _8_ and, in the language of the art, is called
the _double dog_. As will be seen, it has two retaining fingers, one
adapted to engage the vertical ratchet and the other, the rotary ratchet
on the selector shaft. This double dog is pivoted at _9_ and is
interlinked in a peculiar way with the armature of the vertical magnet,
the armature of the release magnet, and the arm of the side switch. The
function of this double dog is to hold the shaft in whatever vertical
position it is moved by the vertical magnet and then, when the rotary
magnet begins to operate, to hold the shaft in its proper angular
position. It will be noted that the fixed dog _10_ is ineffective when
the shaft is in its normal angular position. But as soon as the shaft is
rotated, this fixed dog _10_ becomes the real holding pawl so far as the
vertical movement is concerned. The double dog _8_ is normally held out
of engagement with the vertical and the rotary ratchets by virtue of the
link connection, shown at _11_, between the release magnet armature and
the rear end of the double dog. On the previous release of the switch
the attraction of the release magnet armature permitted the link _11_ to
hook over the end of the dog _8_ and thus, on its return movement, to
pull this dog out of engagement with its ratchets. This movement also
resulted in pushing on the link _12_ which is pivoted to the side switch
arm _5_, and thus the return movement of the release magnet is made to
restore the side switch to its normal position. In order that the double
dog may be made effective when it is required, and in order that the
side switch may be free to move under the influence of the private
magnet, the double dog is released from its connection with the release
magnet armature by the first movement of the vertical magnet in a manner
which is clear from the drawing.

=First Selector Operation.= In discussing the details of operation of
the various selectors it will be found convenient to divide the
discussion according to the position of the side switch. This will bring
about a logical arrangement because it is really the side switch which
determines by its position the sequence of operation.

[Illustration: Fig. 393. Front View of Connector]

_First Position of Side Switch._ This is the position shown in Fig. 390,
and is the normal position. The vertical and the rotary lines extending
from the ca