. Electrical world. s were not exactly balanced, the impedance would be a littlegreater than R, but not much even then, because )i if; comparativelylow, not over about 15 per second. While the above is true of slowly changing currents, it does notapply to extreme high-frequency currents. The core of coil D formsa complete magnetic iron circuit, and is large and massive, whichmakes it sluggish. This prevents a complete reversal of its mag-netism throughout the whole core when the very high-frequencytelephone currents tend to reverse it; therefore, instead of one com-plete magentic circuit we ha
. Electrical world. s were not exactly balanced, the impedance would be a littlegreater than R, but not much even then, because )i if; comparativelylow, not over about 15 per second. While the above is true of slowly changing currents, it does notapply to extreme high-frequency currents. The core of coil D formsa complete magnetic iron circuit, and is large and massive, whichmakes it sluggish. This prevents a complete reversal of its mag-netism throughout the whole core when the very high-frequencytelephone currents tend to reverse it; therefore, instead of one com-plete magentic circuit we have two. The lines of force set up ineach coil find a return path through the air rather than through theiron; moreover, the two coils oppose each other inductively, whichfurther tends to make each coil and its core act as an independentimpedance coil. Such being the case, we have two similar im-pedance coils in series to oppose the telephone current. The im-pedance of the two coils in series is given by the formula:. FIG. II.—TICKET WIRE TPER.\TOR .\ND L0.^01ER.\T0RS. -DIST.\NCE TELEPHONE pedance coils and telegraph fnstruments, should be from (6) toten (10) microfarads. The greater the capacity of these condensers,the less the disturbance in the telephone circuit from the telegraph. It is sometimes advisable to bridge the telegraph key with a two(2)-microfarad condenser, which absorbs the sudden rise of poten-tial due to the self-inductance of the line and coils when the circuitis broken by the key, thus preventing a sharp fluctuation on the linetending to cause a disturbance in the telephone set. V[2R -{- 2 7?)- + (2T7 „/. — 2 •^ 11 /,)-= 1 (/?)- + (4 7!-n L) proper arrangement of condensers and their capacity is also
Size: 1597px × 1565px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectelectri, bookyear1883
