. American telephone practice . is meter has no electrical connection whateverwith the system, its entire function being mechanical. In another device manufactured by the Gray Company no keyis required, the subscriber merely pressing aTmtton on the front ofthe box when told to do so by the operator, this action ringing thebell and registering one count on the meter. One of these devices 476 AMERICAN TELEPHONE PRACTICE. is shown in Fig. 347. The method of securing this to a portabledesk stand is shown in Fig. 348. These devices are simple and effective, but are subject to the samedisadvantages
. American telephone practice . is meter has no electrical connection whateverwith the system, its entire function being mechanical. In another device manufactured by the Gray Company no keyis required, the subscriber merely pressing aTmtton on the front ofthe box when told to do so by the operator, this action ringing thebell and registering one count on the meter. One of these devices 476 AMERICAN TELEPHONE PRACTICE. is shown in Fig. 347. The method of securing this to a portabledesk stand is shown in Fig. 348. These devices are simple and effective, but are subject to the samedisadvantages as those coin collectors which have no electrical con-nection with the central office, the principal one of which is theamount of attention required by the operator to assure the properregistration of the meter. This fault is largely remedied in a classof meters which, like the Scribner and Stroud coin collectors, arepartially controlled by the central office operator. Prominent in this class is the device of H. V. Hayes, which. FIG. PUSH-BUTTON METER. consists of an electro-magnetically operated meter placed at eachsubscribers station, the operating coil of the meter being placed ina bridge of the telephone line which includes the talking device is adapted to use on common battery lines, and there-fore the coil of the meter receives current whenever a subscriberremoves his receiver from its hook for the purpose of sending acall. One impulse of the armature lever, however, will not affectthe registration on the meter dial. In order to cause a registration,therefore, two impulses are required, one in one direction and one inthe other, these impulses always occurring in the same order. Foraccomplishing this, the armature of the controlling magnet is polar-ized so as to move in one direction when the coil is traversed bv a MEASURED SERVICE. 477 current of one polarity, and in the other when the current flows inthe opposite direction. The source of current
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