erator has, therefore, been
automatically cut out of the circuit. He also has removed his receiver
from its hook, thus bringing his talking apparatus into the line
circuit. The operator on the other hand has inserted one of the plugs
_P__{a} into the jack. This action has resulted in the breaking of the
circuit through the drop by the raising of the spring _1_ from the
anvil _3_, and also in the continuance of the line circuit through the
conductors of the cord circuits. Thus, the upper limb of the line is
continued by means of the engagement of the tip spring _1_ with the
tip _4_ of the plug to the conducting strand _6_ of the cord circuit;
likewise the lower limb of the line is continued by the engagement
of the thimble _2_ of the jack with the sleeve contact _5_ of the plug
_P__{a} to the strand _7_ of the cord circuit. The operator has also
closed her listening key _L.K._ In doing so she has brought the
springs _8_ and _9_ into engagement with the anvils _10_ and _11_ and
has thus bridged her head telephone receiver with the secondary of her
induction coil across the two strands _6_ and _7_ of the cord.
Associated with the secondary winding of her receiver is a primary
circuit containing a transmitter, battery, and the primary of the
induction coil. It will be seen that the conditions are now such as to
permit the subscriber at the calling station to converse with the
operator and this conversation consists in the familiar "Number
Please" on the part of the operator and the response of the subscriber
giving the number of the line that is desired. Neither the plug
_P__{c}, nor the ringing key _R.K._, shown in Fig. 242, is used in
this operation. The clearing-out drop _C.O._ is bridged permanently
across the strands _6-7_ of the cord, but is without function at this
time; the fact that it is wound to a high resistance and impedance
prevents its having a harmful effect on the transmission.

[Illustration: Fig. 242. Operator Answering]

It may be stated at this point that the two plugs of an associated
pair are commonly referred to as the answering and calling plugs. The
answering plug is the one which the operator always uses in answering
a call as just described in connection with Fig. 242. The calling plug
is the one which she next uses in connecting with the line of the
called subscriber. It lies idle during the answering of a call and is
only brought into play after the order of the calling subscriber has
been gi