n between the two parties is then established,
and no one else can in any possible way, except by permission of the
operator, obtain access to the line.

It is obvious that some means must be provided for restoring the
selecting relays to normal after a conversation is finished. By
referring to Fig. 194 it will be seen that the upper end of the latch
spring _5_ is bent over in such a manner that when the armature is
attracted by current flowing through the coil _7_, the knob on the
left-hand end of the armature on rising engages with the bent cam
surface and forces back the latch, permitting spring _2_ to return to
its normal position.

To restore the line the operator sends out sufficient additional
selective impulses to extend the circuit to the end of the line, and
thus brings the grounder into circuit. The winding of the grounder is
connected in such a manner that the next passing impulse throws off
its latch, permitting the long spring to contact with the ground
spring. The operator now sends a grounded impulse over the continuous
limb _L_ of the line which passes through the restoring coils _7_ at
all the stations and through the right-hand coil of the grounding
device to ground. The selecting relays are, therefore, simultaneously
restored to normal. The grounder is also energized and restored to its
normal position by the same current.

If a party in calling finds that his own line is busy and he cannot
get central, he may leave his receiver off its hook. When the party
who is using the line hangs up his receiver the fact that another
party desires a connection is automatically indicated to the operator,
who then locks out the instrument of the party who has just finished
conversation and passes his station by. When the operator again throws
the key, the waiting subscriber is automatically selected in the same
manner as was the first party. If there are no subscribers waiting for
service, the stop relay at central will not operate until the grounder
end of the line is unlatched, the selecting relays being then restored
automatically to normal.

The circuits are so organized that at all times whether the line is
busy or not, the movement up and down of the switch hook, at any
sub-station, operates a signal before the operator. Such a movement,
when made slowly and repeatedly, indicates to the operator that the
subscriber has an emergency call and she may use her judgment as to
taking the line away from the pa