. American telephone practice . d R W, are opposite their respective rowsof contacts corresponding to the trunk lines leading to the propergroup of second selectors. Immediately afterwards, the rotary re-lay, R R, will receive one impulse due to the grounding of thespring, 2 (Fig. 511), and as a result of the attraction of its armaturethe private magnet will operate to attract and release its armatureonce. The contacts carried by the private magnet will not in this 714 AMERICAN TELEPHONE PRACTICE. case effect any circuit changes, since the circuit from its armature isopen at the vertical relay
. American telephone practice . d R W, are opposite their respective rowsof contacts corresponding to the trunk lines leading to the propergroup of second selectors. Immediately afterwards, the rotary re-lay, R R, will receive one impulse due to the grounding of thespring, 2 (Fig. 511), and as a result of the attraction of its armaturethe private magnet will operate to attract and release its armatureonce. The contacts carried by the private magnet will not in this 714 AMERICAN TELEPHONE PRACTICE. case effect any circuit changes, since the circuit from its armature isopen at the vertical relay. The movement of the private magnetarmature will, however, through its escapement, allow the sideswitch to move to its middle point. The circuit is now that of Fig. 515, and from this it will be seenthat the circuit of the rotary magnet is completed through the fifthside-switch lever, the battery, B, and the interrupter, /. The rotarymagnet thus receives a number of impulses in rapid succession, and <^—l SUBSTATIONCALLINQ. FIG. 515.—FIRST SELECTOR DURING TIME OF ACTION. as a result of each one the shaft and its wipers are stepped aroundover the horizontal row of trunk line contacts. In view of the fact that the wiper contacts connected with thetrunk lines are multipled to other switches, it is evident that someof the trunk lines, represented by the contacts over which the rotarymagnet is now causing the wipers to sweep, may be busy at otherswitches. It is the function of the rotary magnet, therefore, tomove the wipers until they engage the contacts of the first idle trunk,and for the purpose of illustration let it be assumed that the firsttwo trunk lines of the selected horizontal row are busy at this a trunk is busy its private bank contacts are grounded at theswitch at which the trunk is made busy in a manner that will be AUTOMATIC SWITCH-BOARD SYSTEMS. 715 explained. The first two private wiper contacts of the switch thatis being rotated are therefore in Fi
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