pose but this is assumed to be
the first one found idle by the second selector.

_Connector Action._ The third movement of the subscriber's dial will
send but one impulse, this corresponding to the _first_ group of ten in
the _second_ hundred in the _third_ thousand. This impulse will move the
connector shaft up to the first level of bank contacts; and from now on
the action of the connector differs radically from that of the
selectors. The connector is not searching for an idle trunk in the group
but for a particular line and, therefore, having chosen the group of ten
lines in the desired hundred, the connector switch waits for further
guidance from the subscriber. This comes in the form of the final set of
impulses sent by the subscriber's signal transmitter which, in this
case, will be three in number, corresponding to the final digit in the
number of the called subscriber. This series of impulses will control
the rotary movement of the connector wipers which will move along the
first level and stop on the third one. The process is seen to be one of
successive selection, first of a large group, then of a smaller, again
of a smaller, and finally of an individual.

If the line is found not busy, the connection between the two
subscribers is complete and the called subscriber's bell will be rung.
If it is found busy, however, the connector will refuse to connect and
will drop back to its normal position, sending a busy signal back to the
calling subscriber. The details of ringing and the busy-back operation
may only be understood by a discussion of drawings, subsequently to be
referred to.

=Two-Wire and Three-Wire Systems.= In most of the systems of the
Automatic Electric Company in use today the impulses by which the
subscriber controls the central-office apparatus flow over one side of
the line or the other and return by ground. The metallic circuit is used
for talking and for ringing the called subscriber's bell, while ground
return circuits, on one side of the line or the other, are used for
sending all the switch controlling impulses.

Recently this company has perfected a system wherein no ground is
required at the subscriber's station and no ground return path is used
for any purpose between the subscriber and the central office.
This later system is known as the "two-wire" system, and in
contra-distinction to it, the earlier and most used system has been
referred to as the "three-wire." It is not meant by t