A PAPER on modern communication systems, by Dr. F. Luschen, was read to the Institution of Electrical Engineers on April 7. Dr. Luschen pointed out that the rapid progress of invention has made modern communication systems very complicated to design. Few realise how difficult it was to solve the problem of the interconnexion of wired and wireless systems. This was first carried out in the telephone link between Great Britain and the United States. Further problems that have been solved are the multiple utilisation of lines for telegraphy and telephony, the control of electrical apparatus at a distance, and the electro-acoustic transmission problems involved in broadcasting and sound-films. These methods have widely extended the field of use of communication systems. The information contained in the spoken word is an extremely complicated function of the time. The transmission system is composed of widely different elements. At first, therefore, it appears to be a hopelessly difficult problem. Yet, with the help of a few simple mathematical principles, engineers have succeeded in visualising the transmission of signals. As an illustration of the pitch of perfection to which carrier-current telephony has reached in the United States, Dr. Lüschen described a pole line carrying twenty pairs of conductors, sixteen of which carry three high frequency channels each, in addition to their low frequency communication circuits, while the other four pairs are equipped with ten telegraph channels each. Twenty pairs of wires thus result in 150 communication circuits, 80 of them being telegraph circuits and 70 of them telephone circuits. Dr. Luschen also gave interesting particulars of tests made on a system of telephony and telegraphy linking Berlin with Buenos Aires. It is designed to transmit speech and two telegraphic messages simultaneously.