Short notes on the mechanical arrangements of various storage drums, and the principles of storing and recovering digital information from such drums, are followed by a discussion on transducer design.An optimum transducer design is described, which is suitable for both writing-and reading-head functions. The characteristics of Mumetal and ferrite transducers are discussed, as well as the problems of mounting and screening.The preparation and performance of both nickel-plated and oxide-coated recording surfaces are described, and the results are compared, showing that oxide surfaces are more suitable when high-density storage is required.