Patent GB-794126-A (GB)
Title: Recording equipment for electrical signals
IPC: H04L12/54
Filed: 1955-06-24
Abstract: 794,126. Electric digital-data-storage apparatus. STANDARD TELEPHONES & CABLES, Ltd. June 24, 1955 [June 25, 1954], No. 18346/55. Class 106 (1). In a recording equipment for binary - digit - representing electric signals in which one binary digit is represented by a single change and the other digit by no change, as set out in Specification 766,318, an additional change is produced in response to a predetermined number of consecutive other digits. As described, the digits are recorded on a magnetic drum, e.g. for an electronic digital computer, and the additional changes are recorded when necessary to make the maximum time between record changes 2T (where T is a digit time interval) and thus prevent spurious signals being obtained when reading, e.g. by means of the circuit described in Specification 766,317, [Group XL (b)]. Fig. 1 shows a recording circuit in which each " 0 " is represented by a change in direction of current through record winding H and a " 1 " by no change. A binary number to be recorded, such as i, Fig. 11, is stored on a pattern counter PC, e.g. similar to the circuit described in Specification 663,574, [Group XL (b)]. For recording, a signal is applied to terminal A which opens and closes gates G3, G4, respectively, whereby the next pulse s, Fig. 11, at S will switch bi-stable multivibrator EJ, so that it opens gate G5 (which may be as described in Specification 780,831) immediately and gate G1 through G2 which is inhibited by blocking pulses b, Fig. 11, at B. The pulses s define sectors of the magnetic drum, and the pulses b blank periods at the beginning and end of a sector. The pulses d, synchronized with the rotation of the drum, are supplied via D and G1, to step out the number stored in PC. The output pulses do (one for each " 0 "), corresponding to i, each switch over bi-stable multivibrator EJ2 whose two output leads are connected via G5 and winding H, thus recording pattern PI, Fig. 11, on the drum; Fig. 2 comprises a portion PR identical with that of Fig. 1, and includes an additional gate G6 which receives the pulses d and is inhibited by pulses do, whereby pulses d1, Fig. 11, are obtained. The pulses d1 are delayed in device T T1 by - (pulses d<SP>1</SP>1) so that they are recorded 2 out of phase with pulses do (pattern P2, Fig. 11). Since this makes the minimum time interval T between successive record changes -, this 2 system requires twice as much recording space as that of Fig. 1. According to the invention, this difficulty is avoided by applying pulses dl through a gate G7 controlled by pulses do. In Fig. 3, for example, comprising portions SR, PR identical with those of Figs. 2 and 1, pulses do are delayed in device T2 by T (pulses d<SP>1</SP>0) and inhibit gate G7 whereby a pulse d1 is recorded only if there was no pulse do in the preceding digit interval (pattern P3, Fig. 11); due to the time lag of pulses d<SP>1</SP>0, sector pulses s 1 are used in place of s. Another form, Fig. 5, in which pulses do are recorded after being T delayed in T1 by - (pulses d<SP>11</SP>0) and are further 2  T delayed by - in T<SP>1</SP>1 before being applied to G7 2 which lies in a direct recording path for pulses d1, provides record pattern P4, Fig. 11. Other arrangements of delay devices are described, the devices being, e.g., artificial or magnetostrictive lines or phantastron circuits. In Fig. 8, the devices T1, T<SP>1</SP>1 are replaced by monostable multivibrators FF, FF<SP>1</SP>. Pulses do switch over FF to its unstable condition in which it opens gate G8 whereby corresponding pulses d<SP>1</SP>, Fig. T 11, phase-shifted from d by -, are applied from 2 D1 to similarly switch over FF1 to inhibit G7. Other arrangements employing bi-stable multivibrators also are described.