. American telephone practice . TION EQUIPMENT. 305 at the central office would necessarily be adjusted so as not to workthrough 10,000 ohms, but to respond properly when the shunt cir-cuit through the transmitter and receiver was closed around the callbell, as when the telephone is in use. This was the arrangement first proposed, and used to some extentin early common battery work. It proved faulty, however, for thefollowing reasons: The constant flow of current from the centraloffice battery through the call bells made necessary a marginal ad-justment of the relays at the central office, and
. American telephone practice . TION EQUIPMENT. 305 at the central office would necessarily be adjusted so as not to workthrough 10,000 ohms, but to respond properly when the shunt cir-cuit through the transmitter and receiver was closed around the callbell, as when the telephone is in use. This was the arrangement first proposed, and used to some extentin early common battery work. It proved faulty, however, for thefollowing reasons: The constant flow of current from the centraloffice battery through the call bells made necessary a marginal ad-justment of the relays at the central office, and also proved a con-stant drain on the storage batteries, especially severe when a largenumber of lines were served. These defects are removed by placing a condenser in series withthe bell, in which case the extremely high winding of the coils is un-necessary, 1000 ohms being ample. The circuit arrangement with thecondenser added then becomes that shown in Fig. 255. While the addition of the condenser in this manner removes com-. FIG. SUB-STATION CIRCUIT WITH CONDENSER. pletely the difficulties due to the waste of current and to the marginaladjustment of the central office relays, it leaves several undesirablefeatures with respect to the talking apparatus. This is due to thefact that the direct current which supplies the transmitter passes alsothrough the receiver coils. Unless, therefore, a receiver is properlypoled; that is, placed in the circuit of the line in such mannerthat the steady flow of current through it increases rather thandiminishes the strength of its magnets, a serious loss of talkingefficiency results. Very often when the receiver is wrongly placedin the line, the flow of current through it proves about sufficient toneutralize the effect of the permanent magnets, thus almost com-pletely destroying the effectiveness of the receiver. This disad-vantage does not exist if the receivers are placed in the line so thatthe current strengthens rather than we
Size: 2395px × 1043px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., boo, bookcentury1900, bookdecade1900, bookidamericantelepho00mill
