Modern developments in telephone transmission

In being called upon to reply to the discussion on my paper, I find myself somewhat at a loss; as with the exception of Captain McArthur's valuable contribution, which materially enhanced the value of that portion of the paper dealing with amplifiers, there was no discussion. It has been suggested that perhaps the subject was too wide for a single paper to cover, but this would increase the scope of possible discussion. I did hope at least that some of our mathematical friends would fall foul of my notation, as I am old-fashioned enough still to denote electrostatic capacity by K, and cannot bring myself to denote current by I, but I was disappointed. Since the paper was written, the results of further development work have been published, notably the commercial introduction of multiplex telephony by carrier currents, and the improvement in loading coil efficiency by the use of cores of compressed powdered iron. A striking development in combined line and radio transmission was described in Messrs. Clement, Ryan and Martin's paper on "The Avalon-Los Angeles Radio Toll Circuit," read before the New York Institute of Radio Engineers in May last. This circuit provides telephonic communication between Avalon, Santa Catalina Island, off the coast of California, and the Bell Telephone System of the mainland, part of the circuit being completed by radio transmission across the San Pedro Channel, the length of the "radio-link" being 31½ miles. It should be remembered that this circuit is not merely a demonstration of what can be done, hut is in every-day commercial use.