. Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems . e subscriber. It alsounlocks control relay R-13, as well as stopping relay R-5 of the primarydistributor (Fig. 222). When this latter relay falls back, current iscut off from relay R-ll of the secondary distributor. This allows relayR-9 to fall back and take the negative battery potential from wire 98 AUTOMANUAL SYSTEM 263 and row test contact $-82 of the secondary selector. The primary andsecondary distributor switches are therefore returned to common use sothat any other subscriber in the same hundred m
. Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems . e subscriber. It alsounlocks control relay R-13, as well as stopping relay R-5 of the primarydistributor (Fig. 222). When this latter relay falls back, current iscut off from relay R-ll of the secondary distributor. This allows relayR-9 to fall back and take the negative battery potential from wire 98 AUTOMANUAL SYSTEM 263 and row test contact $-82 of the secondary selector. The primary andsecondary distributor switches are therefore returned to common use sothat any other subscriber in the same hundred may initiate a call. The unlocking and falling back of the contl relay 72-13 of the priminaryselector (Fig. 224) takes the negative battery potential from wire 45 sothat any other key-set switch will not stop on this trunk. The pullingup of the signal relay 72-34 (Fig. 225) at the operators position, lights aguard lamp L-2 (Fig. 227) which attracts the attention of the also rings a night alarm bell for night service, if desired, and operates acall register, E. d d d d2 d5 d. Fig. 227.—Sending machine and keyset circuit. The operator now answers the call by pressing the listening key L-K(Fig. 227). Current then flows from ground (Fig. 181) contact of keyL-K and wire 125 to (Fig. 225) winding of listening relay 72-33, backcontact of relay 72-31, back contact of relay 72-30 to negative listening relay immediately pulls up and locks itself to ground. Itbreaks the circuit of the trunk cut-off relay 72-42 (Fig. 224), which fallingback connects the talking circuit to the operators position. The signalrelay is also de-energized so that the lamp L-2 is extinguished. The listen-ing relay also connects the operators set to the line. The operator now speaks to the subscriber and obtains the desirednumber, which she sets up on the rows of keys shown in Fig. 227. The 264 AUTOMATIC TELEPHONY row of keys marked K-l indicates the thousands digit, K-2 the hun-dreds digit
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttelephone, bookyear19
