Abstracts of Bell System Technical Papers Not Published in This Journal (01 January 1952)

Elec. Eng., 70, pp. 692-093, Aug. 1951. Low terminal costs and single-cable operation make this the first economically practical carrier system for medium-haul telephone circuits. Performance is not sacrificed for economy. .15-Kw 500-Mcgacycle Grounded-Grid Tridode* C. E. FAY1, D. A. A. HALE1, a n d R. J. KIRCHER1. Proc. I.R.E., 39, pp. 800-803, July , 1951. 

A Short-Cut Method Aids Figuring Exhaust and Collecting Systems. W. H. FOGLE3. Heating, Piping and Air Cond., 23, p p . 75-78, July , 1951. A simple, workable method of determining static losses in industrial exhaust and collecting systems is explained here by means of a sample problem and its step-by-step solution. The method might be described as an "averaging out" process, whereby all duct sizes anil lengths are averaged out with the cfm and velocity to give a total linear footage of the average duct size and an average velocity. Arcing at Electrical Contacts on Closure. Part I. Dependence Upon Surface Conditions and Circuit Parameters * L. I I . 

GERMER1. Jl. Appl. Phys. 22, pp. 955-964, July , 1951. In a low-voltage circuit the occurrence of an arc between approaching electrodes is dependent upon the nature of the surfaces and upon the circuit inductance. For carbon surfaces, or noble metal surfaces which have been "activated" by operation in various organic vapors resulting in a carbonaceous layer, the limiting circuit inductance is somewhat above 10~3h, which is much higher than the limiting inductance for clean noble metal surfaces.