nt through the back release magnet; and, of
equal importance, it places a ground on the private bank contact of that
trunk so that the private wiper of any other switch will be prevented
from stopping on the contacts of this trunk in the same manner that the
wiper of this switch was prevented from stopping on other trunks that
were already in use.

The fourth lever on the side switch, when in its third position, serves
merely to close the circuit of the rotary off-normal lamp. This lamp is
for the purpose of calling attention to any first selector switch that
has been brought into connection with some second selector trunk and
which, for some reason, has failed in its release. These off-normal
lamps are so arranged that they may be switched off manually to avoid
burning them during the hours of heaviest traffic. At night they afford
a ready means of testing for switches that have been left off-normal,
since the manual switches controlling these lamps may then be closed,
and any lamps which burn will show that the switches corresponding to
them are off-normal. Simple tests then suffice to show whether they are
properly or improperly in their off-normal position.

_Release of the First Selector._ As will be shown later, the normal way
of releasing the switches is from the connector back over the release
wire. It is sufficient to say at this point that when the proper time
for release comes, an impulse of current will come back over the second
selector trunk release wire through the private wiper, to the back
release relay magnet, and thence to ground through the third wiper of
the side switch which is in its third position. It may be asked why the
back release magnet was not energized during the previous operations
described, when current passed through it. The reason for this is that
in those previous operations the private magnet was always included in
series in the circuit and on account of the high resistance of the
private magnet, sufficient current did not pass through the back release
magnet to energize it.

When the back release relay is energized, it closes the circuit of the
release magnet and thus, through the link _11_, draws the double dog
away from its engagement with the shaft ratchets and at the same time,
through the link _12_, restores the side switch to its normal position.
Whenever the release magnet is operated it acts as a relay to close a
pair of contacts associated with it and thus to momentarily