NEW RECORDING MEDIUM .j8 I 



liability (h^sircd in the new tip})li(';i(ion.s, and attention wa« therefore 

 directed to two new elasses of ma^netie reeordinp; media whieh have l)een 

 dcNcloped in recent years. These are the (>lect I'opialed media and the 

 powdered mecha. 



In recent years magnetic recording metlia iiave been connnercially 

 produced by an electroplating process by the Brush Development C'om- 

 pany of Cleveland, Ohio. Evaluation by Bell Telephone Laboratories 

 shows that such a plating does not easily deteriorate, gives a relatively 

 iiigh signal output and is capable of excellent transmission character- 

 istics. But in order to realize consistently satisfactory transmission, it 

 is necessary to maintain intimate contact between the recording medium 

 and tlu^ magnetic recording and reproducing heads. The expense of 

 ])r()\iding the relatively precise mechanisms necessary to obtain the 

 d(>sired performance objectives suggested the exploration of other media 

 which might simplify this problem. 



The powdered magnetic media have evolved from German work dating 

 back to about 1932 and from American work since about 1941. In these 

 media the active magnetic material is a finely divided ferro-magnetic 

 powder, usuall}^ iron oxide. This is usually applied with a binder as a 

 surface coating on a tape of plastic or paper, but the Germans at one 

 time produced a tape which was a homogeneous mixture of oxide and 

 plastic. In their present state of development, media of this type offer 

 excellent transmission characteristics and are relatively economical. In 

 the past four or five years they have found widespread commercial appli- 

 cation in the form of coated tape in all fields of recording and transcrip- 

 tion work. 



Attempts were made to employ commercial types of these coated tapes 

 in various forms of continuous-loop mechanisms, but none met the de- 

 sired recjuirements in regard to life, reliability, and flexibility of oper- 

 ation. An analysis of the experimental results indicated that most failiu'es 

 were due to physical failure of the media as a result of the tension, 

 flexion and abrasion to which they were subjected, but the magnetic 

 records were substantially undeteriorated even wdien physical failure of 

 the supporting base occurred. 



It became apparent that a specialized recording medium would have 

 to be developed to meet the Bell System requirements for transcriV)ed 

 message services. Development effort was concentrated on the field of 

 powdered media, because these media offered attractive transmission 

 properties and because the expanding commercial importance of this 

 field promised a continuing industrial development and production pro- 

 gram which would provide an economical source of high equality magnetic 



