Lays done preferred electrical values for the interconnection of sound system components. Covers reference documents, D.C and A.C power supply voltages and frequencies, power supply feeding microphones, connections and connectors, marking, matching of microphones and amplifiers, matching of record playing units and amplifiers, matching of tuners and amplifiers, matching of amplifiers and amplifiers, matching of magnetic tape recorders and amplifiers, matching of auxiliary equipment and amplifiers, matching of loudspeakers and amplifiers, matching of headphones and amplifiers and auxiliary passive elements.