Patent GB-917451-A (GB)
Title: Data translator
IPC: G11B5/86
Filed: 1961-11-20
Abstract: 917,451. Magnetic drum data stores. SPERRY RAND CORPORATION. Nov. 20, 1961 [Nov. 22, 1960], No. 41489/61. Class 106 (1). In an arrangement for recording digital data on a magnetic drum, an initial marker pulse is recorded on the drum to establish the position of the first item of data, which is then recorded, a pair of marker pulses is recorded at diametrically opposite points spaced from the initial pulse, the initial pulse and one of the pair of pulses are erased and a second item of data is recorded at a position related to the remaining marker pulse. Further items of data are recorded in accordance with this scheme. The arrangement described is for transferring data a from a magnetic tape to a magnetic drum, the circumference of which can store 2,400 digits, each character being stored as a combination of four binary digits in parallel tracks. Twelve characters constitute a word, so that 200 words can be stored on the drum circumference. Characters read from the tape (not shown) are applied to a register 30 and when a complete word is registered it is transferred to another one-word register 132 from which it is recorded on the drum (not shown in Fig. 1) by heads 106(A) or 108(B) as determined by the marker pulses.  Operation. A " start " signal applied to a tape drive switch 10 starts the tape drive and sets a " start operations " switch 14 and an " odd-even " switch 16 which provides an enabling signal to gates 58, 62. The output of the switch 14 is applied to a gate 24 so that when word time 198 occurs, an " initial clear " switch 28 is set to cause a head 42 to write zeros on the marker pulse track, thereby clearing it. A gate 26 then resets the switch 28 and provides a pulse to cause a " 1 " marker pulse Ml to be written by the B marker head 42. When a data word has been read into the register 30, a sprocket counter 32, actuated by the tape drive, produces an output which triggers the switch 16 to enable gates 60, 64, the output from the counter 32 also setting a switch 34 whose output shifts the data from the register 30 to the register 132. Assuming that the marker pulse M1 is read by the A head 48, Fig. 4a, gates 58, 64 and 88 are enabled, the output of the gate 88 resetting an " erase marker " switch 94 to apply a signal to a gate 98. The gate 64 is opened and sets a " select head B " switch 70 to open gates 112, the output of the gate 64 also causing transfer of data from the register 132 to the B heads 108, thereby effecting recording of one word on the drum, Fig. 4b. Gate 64 applies a signal to a delay 76 which can be varied to permit either sequential or interlaced recording of words on the drum. Subsequent to the first word being written on the drum, an output from the delay 76 causes the " 1 " marker pulse to be written simultaneously by the heads 42, 48, only the pulse M2, recorded by the head 42, being shown in Fig 4c since the pulse recorded by the head 48 is subsequently erased, together with the pulse M1 under the control of the " erase marker " switch 94. The next word is recorded by the " A " heads or the " B " heads according as the marker pulse M2 is read by the head 48 or the head 42, Figs. 4d-4e. Subsequently, Fig. 4f, the marker pulse M3 is written and the pulse M2 erased. When the marker pulse M3 is read by the A marker head 48, the third word is recorded by the B recording heads (upper parts of Figs. 4g, 4h), but when the pulse M3 is read by the B marker head 42, the third word is recorded by the A recording heads (lower parts of Figs. 4g, 4h). Thus, the odd-numbered words are recorded by a set of heads opposite to the head that read the marker pulse whereas the even-numbered words are recorded by the heads adjacent to the head which read the marker pulse.