. American telephone practice . the subscribers operators from knowing when the chief oper-ator listens in on their circuits. Operators become very skilled innoticing any changes in the sound of their circuits, and would at once 632 AMERICAN TELEPHONE PRACTICE. observe the effect of any other transmitter being connected withtheir telephone sets. As illustrating the astute methods sometimes employed by theregular operators to ascertain whether or not they are being watched,it may be mentioned that in some cases where nickel-plated frontshave been provided for the operators transmitters, these h
. American telephone practice . the subscribers operators from knowing when the chief oper-ator listens in on their circuits. Operators become very skilled innoticing any changes in the sound of their circuits, and would at once 632 AMERICAN TELEPHONE PRACTICE. observe the effect of any other transmitter being connected withtheir telephone sets. As illustrating the astute methods sometimes employed by theregular operators to ascertain whether or not they are being watched,it may be mentioned that in some cases where nickel-plated frontshave been provided for the operators transmitters, these have beenkept carefully polished and used as a mirror, by which the operatorcould observe the actions of the chief, seated behind her. This isone reason for the usual black finish of the operators transmitters. In Fig. 461 is shown one of the chief operators service observa-tion lines. These lines are normally terminated at open clips on the 11 MULTIPLE JACKS < TEMPORABY JUMPERS ■__£ ( fL™. m INTER. DI3T. FRAME. 25llft fiSl CHIEF OFTV5. irse MULTIPLE PO\RD. FIG. 462.—METHOD OF CONNECTING LINE FOR OBSERVING SERVICE. intermediate distributing frame, and by means of three-wire jumpers,any one of them may be connected to any subscribers line. Aregular Western Electric line circuit so connected by means of atemporary jumper wire to a service observation circuit on the chiefoperators desk is shown in Fig. 462. When the subscriber on such a line calls the lamp, A, will belighted, that lamp being connected between the live side of batteryand the regular line lamp terminal on the intermediate frame, thetwo lamps thus being lighted in multiple by the action of the linerelay. The chief operator, by inserting the plug of one of the cir-cuits shown in Fig. 460, will place her telephone in a bridge of CHIEF OPERATORS AND MONITORS EQUIPMENTS. 633 the subscribers line, cutting off the remaining portions of theobservation circuit apparatus at the cut-off jack,
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