INDUCTIVE LOADING FOR TELEPHONE FACILITIES 759 



is used in pamllel with a wire-wound condenser. In such combinations, the 

 precision capacitance-adjustments are made with the wire-wound condenser. 

 The nominal capacitances of the mica condensers range from 500 mmf to 

 4500 mmf. 



Prior to the development of these small splice-installation types of build- 

 ing-out condensers (during the late 1930's), building-out stub cables were 

 extensively used in the loading-section capacitance adjustments. Several 

 pairs in these stubs were connected in parallel for use with an individual 

 main cable pair. By varying the number of parallel pairs, and the length of 



J) 



Fig. 33 — Solenoidal type non-magnetic core loading coil used for type J carrier loading. 

 At right: Internal coil structure and supports; At left: Copper shielding-container, with 

 coil inside. This view shows the terminal strip on which the coil terminal clips are mounted, 

 and also one of the brackets used in fastening the coil in position in the loading coil cases. 



the stub cable, the necessary wide range of building-out capacitance was 

 obtained with the required degree of precision. 



Type J Loading 



Full-Weight Loading Coils: The full-weight loading coils are small sole- 

 noidal- type, air-core coils having a layer- type winding with a very finely 

 stranded conductor, for control of coil resistance at the high ''J" frequencies. 

 The outside diameter and axial length are 2f inches and 0.5 inch, respec- 

 tively. To contain the external magnetic field, and control modulation effects 

 and intercoil crosstalk that would otherwise result, a relatively large shielding 

 container is required. Its over-all diameter is about 5f inches and its axial 



