Fig. 241. Subscriber Calling
[View full size illustration.]

Operator Answering. The next step is for the operator to answer the call and this is shown in Fig. 242. The subscriber has released the handle of his generator and the generator 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 Pa 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 Pa 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 Pc, 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.

Fig. 242. Operator Answering
[View full size illustration.]

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 given, in which case it is used in establishing connection with the called subscriber.