An 17/8-IPS magnetic recording system for stereophonic music

The primary aim of this work has been to develop a stereophonic system for recorded music, using a small, inexpensive and practical cartridge with magnetic tape as the information carrier. In order to make the cost of the recorded cartridge comparable with a disk containing an equivalent amount of music, it was realized that basic developments in magnetic recording such as efficiency of recording and reproducing techniques were necessary to meet the packing density requirements. This paper describes developments which have led to a recorded cartridge one fifth of the volume of a disk and capable of playing more than one hour of stereophonic sound uninterrupted. In order to obtain the desired signal-to-noise ratio and frequency response to 15 kc, radical improvements have been made to tape, recording system and playback head. In conjunction with this work, a fully automated tape machine has been developed. The machine is equipped with a changer-type mechanism and accommodates a number of cartridges which are played and rewound completely automatically, one after another, furnishing music for several hours. The machine requires no manual threading and has a rewind cycle of less than twenty seconds for an hour-long tape.