Abstract: A transmitting/receiving system and a receiving apparatus wherein a plurality of information signals having mutually different frequency bands processed through predetermined modulation are transmitted in time series from a transmitting apparatus via an electric power line. A desired information signal is selected out of the plural transmitted information signals, and the transmission quality of the selected information signal is measured. When the result representing the measured transmission quality is low, the signal being currently received is switched to the information signal having another frequency band indicating a better transmission quality.

Abstract: Program segments on a magnetic tape are identified by recording patterns of continuous sine wave signal bursts and blank portions in non-recorded spaces between the program segments, the continuous sine waves all having the same low-frequency relative to the audio frequency band and a selected number of continuous sine waves and a corresponding blank portion of the same length each form one level of a binary signal and a second burst of continuous sine waves and a corresponding blank portion of the same length each form the other level of the binary signal. These four elements are arranged to provide an individual address code for each of the program segments on the magnetic tape and are arranged such that they may be read in either direction of tape travel, in order to identify the program segment from either direction, by forming the address code signals as complementary pairs based upon the location of the program segments relative to the ends of the tape.