which is of such depth as to
permit the pawl _6_ to fall so far into the segment as to allow the
rocker arm _2_ to close both the talking and the ringing circuits.
Besides the moving pawl _6_ there is a detent pawl _7_. This always
holds the segment _3_ in the position to which it has been last moved
by the moving pawl _6_.

The actuating magnet _1_, as has been stated, is polarized and when
energized by currents in one direction, the rocker arm moves the pawl
_6_ so as to step the segment one notch. When this relay is energized
by current in the opposite direction, the operation is such that both
the moving pawl _6_ and the detent pawl _7_ will be pulled away from
the segment, thus allowing the segment to return to its normal position
by gravity. This is accomplished by the following mechanism: An
armature stop is pivoted upon the face of the rocker arm so as to swing
in a plane parallel to the pole faces of the relay, and is adapted,
when the relay is actuated by selective impulses of one polarity, to be
pulled towards one of the pole faces where it acts, through impact with
a plate attached to the pole face of the relay, as a limiting means
for the motion of the rocker arm when the rocker arm is actuated by the
magnet. When, however, the relay is energized by current in the
opposite direction, as on a releasing impulse, the armature stop swings
upon its pivot towards the opposite pole face, in which position the
lug on the end of the armature stop registers with a hole in the plate
on the relay, thus allowing the full motion of the rocker arm when it
is attracted by the magnet. This motion of the rocker arm withdraws the
detent pawl from engagement with the segment as well as the moving
pawl, and thereby permits the segment to return to its normal position.
As will be seen from Fig. 189, each of the relay magnets _1_ is
permanently bridged across the two limbs of the line.

Each station is provided with a push button, not shown, by means of
which the subscriber who makes a call may prevent the rocker arm of
his instrument from being actuated while selective impulses are being
sent over the line. The purpose of this is to enable one party to make
a call for another on the same line, depressing his push button while
the operator is selecting and ringing the called party. The segment at
his own station, therefore, remains in its normal position, in which
position, as we have already seen, his talking circuit is closed