s serving that hundreds group of
lines will be grounded through the private wiper of some other
connector. That this is so, may be seen by tracing the circuit from the
private wiper on the shaft to the third side switch wiper which is
grounded in the third position; the other connector that has already
engaged the line will, of course, have its side switch in its final, or
third position. Again, if the line called is busy, because a call has
already been made from this line to some other line, the private
contacts on the connectors corresponding to the line will be grounded,
as will be seen by tracing from the private bank contacts, which are
shown in Fig. 396, through the private wire to the line switch, which is
shown in Fig. 389, and from thence to ground through the springs _19_
and _20_, which are brought together when the line switch is operated.

In any event, therefore, the determining condition of a busy line is
that its private bank contacts on all connectors of its group shall be
grounded. Under the present assumed condition, therefore, the connector
wipers, which have been brought to the bank contacts of the desired
line, will find a ground at the private bank contact. The connector
shaft stops for an instant on the contacts of this busy line and
immediately there follows over the rotary side of the line the
inevitable single rotary impulse. This energizes the rotary relay and
this, as usual, energizes the private magnet. Remembering now that the
connector side switch is in its second position and that the private
wiper of the connector has found a ground, we may trace back from the
private wiper through the third side switch wiper to its second contact;
thence through the contact springs _14_ and _15_, closed by the private
magnet; thence through the release magnet; thence through the contact
springs _16_ and _17_ of the calling battery supply relay to the live
side of the battery. This calling battery supply relay will, at this
time, have its core energized because the coil _18_ is in series with
the rotary relay coil which, as just stated, was energized by the last
rotary impulse. This series of operations has led to the energizing of
the release magnet, and, as a result, the double dog of the connector is
pulled out of the connector shaft ratchets and the shaft and the side
switch are restored to their normal position.

Busy-Back Signal:--The connector has dropped back to normal in all
respects. The cal