Patent GB-879295-A (GB)
Title: Improvements relating to the transfer of data
IPC: G11C19/00
Filed: 1958-10-31
Abstract: 879,295. Magnetic data-storage apparatus. DIRKS, G. Sept. 18, 1959 [Oct. 31, 1958], No. 34988/58. Class 106 (1). Data is written on to the surface of a magnetic drum (it is stated that a disc or tape could be used instead) at approximately the speed at which it is received, an intermediate buffer store providing for variations in the speeds. Fig. 2 shows an intermediate store consisting of three eight-stage shift registers 30-32 which in turn receive data from magnetic tape 1 and pass it on through gates 47/1-16 for recording on the drum 11. The tape read amplifier 7 supplies the input data to gates 33/1-3 and also provides tape-speed clock pulses applied to gates 35/1-3 for use as read-in shift pulses to whichever of the registers is selected by a counter 34. The count in 34 is advanced by one after each eight tape clock pulses by a counter 36, so that 30-32 are filled in turn, and the first output pulse from 36, indicating that the first register 30 is filled, will switch flip-flop 38 to enable a gate 39 so that the next end-ofsector pulse from a track 40 on the drum (there are 16 sectors in each of which eight signals can be recorded) enables gate 45/1 by counter 46, switches off 38 and switches 43 to open gate 44 to the drum clock pulses from track 13. These pulses then shift out the contents of 30 through gate 45/1, the data being recorded on track 10 by one of 16 record heads 48/1-16. While this shift out is proceeding, eight bits of data are being entered from the tape into 31 via 33/2, and the next eight into 32 and so on, and the counter 46 will switch the drum clock pulses to read out from these registers in turn. While the drum sector pulses are received by counters 46 and 49 at the same rate as block tape signals are generated by counter 36, the apparatus will continue to read blocks into 30-32 in turn, and commence reading out each register for recording by the same head 48 at the beginning of the first sector pulse after the register is filled, since the gate 39 will be re-opened by a block pulse from 36 between each sector pulse, and thus the counter 49 which has an add input via 39 and a subtract input direct will be unaffected by simultaneous receipt at its two inputs. If the tape speed falls below that of the drum, so that a drum sector signal occurs before 38 has been set from 36, gate 39 will not be open for this signal, so that 49 will be counted down to switch to the next record head, one sector downstream on the track 10, and gate 44 is not enabled since 43 is switched off by a sector pulse through gate 53, so that at the next read-out of a register (after the next pulses from the 36 and 40) the data can be recorded in its proper place on the track. If the tape runs faster than the drum the read-out of (say) 30 will not commence before 31 is full; the operation can continue without error, however, read-in to 32 taking place while 30 is read out. A counter 50, of capacity equal to the number of blocks to be transferred, switches off a flip-flop 43 to close gate 44 and thus terminate recording when the transfer is complete. If, due to increase in tape speed, two registers are full when read-out from the tape is completed, the gate 39 is not enabled for advance of the count in 46 for recording in the last sector. A pulse is generated for this (and also to prevent counting down of 49) by a flip-flop 52 which is switched on by occurrence of two successive pulses from 36 without an intervening drum sector pulse, and switched off by the last drum sector pulse through 53 to produce a signal on line 54. Fig. 1 (not shown) illustrates a similar but simplified system having a single shift register, bits from the tape amplifier being entered into the last vacant stage, and shifted out by drum clock pulses, and having three spaced recording heads so that if the tape runs slower than the drum recording can be switched to the next head downstream. Both embodiments are better able to deal with lower than with higher tape speeds, so that in practice the tape (which is also driven by the motor that drives the drum) is arranged to run slightly slow. Specification 851,752, which relates t Q  a drum on which information is recorded in interlaced manner in an arrangement of sectors similar to that of Fig. 2, is referred to. Specifications 820,115 and 846,493 also are referred to.