| 摘要 |
571,772. Artificial lines. STANDARD TELEPHONES & CABLES, Ltd. Dec. 1, 1943, No. 20065. Convention date, Aug. 8, 1942. [Class 40 (iii)] An artificial line comprises a permalloy or like strip separated by a strip of insulating material from a grounded strip of conducting material and means for tapping the permalloy strip at any desired point. The strips may be straight, as shown in Fig. 4, the permalloy and insulating strips 40, 41 being wedge-shaped in cross-section to give a more uniform distribution of current. Where the line is short, it is grounded through a resistance 47 equal to the characteristic impedance of the line. In other arrangements -similar strips or, as shown, parallel-sided ones, are bent into a spiral, Fig. 1, in which case the arm 30 for making the adjustable contact is telescopic, or a helix, Fig. 5 (not shown), in which case it is movable along its shaft. In all cases in which the strips are bent, it is necessary to avoid stresses in the permalloy, e.g. by making it very thin and giving a large diameter to the spiral, by extruding it initially so that it builds up in a helical shape or by submitting the bent strip to an annealing process. |
