Patent GB-786021-A (GB)
IPC: G01D15/12
Abstract: 786,021. Digital electric calculating apparatus. DIRKS, G. June 23, 1950 [Oct., 1, 1948], No. 15773/50. Class 106 (1). An electric calculator comprises input means and output means and, for one or more numbers, a computing record means (not tape or wire) in which digit values are represented at respective localities by changes in the electric or magnetic state of the record material, and an electrically-operating arithmetic unit to which digit values from the record means are transferred, denomination after denomination, to effect, under the control of other digit values delivered to the arithmetic unit, result signals which are transferred to the same or other record means. The machines described comprise signal-input and signal-output means, a computing arrangement, and record means. The input and control means may be a keyboard, a magnetic tape, &c., and the output means may be a magnetic tape, disc or drum, the screen of a C.R.T., a printing unit, &c. The computing means may be a magnetizable drum or disc, the screen of a C.R.T. &c. (but not a magnetic tape or wire). Computing is performed by displacing signals on the record means and may be done either during sensing or recording. In a first embodiment the signal carrier or record means comprises a magnetizable disc 7, Fig. 13, rotating relatively to various signal heads 31 ... 65. Clock pulses for the system are derived from a special track on the disc, being picked up either by a magnetic head or by a photo-cell. Some groups of reading heads are interconnected with writing heads via selective switching means, the control of which enables the performance of computing and like operations. The disc 7 is divided into sectors for dealing with successive denominations, Fig. 7c, which shows developments of parts of two of the tracks on the disc, shows how in a track a, the number " 28 " is represented in two sectors (each comprising four times ten " fields "). By relative displacement of a reading head 29 and a writing head 30, connected through an amplifier, the values of digits may be changed during transfer from one track to the other. Figs. 9a and 9b show how the addition 28+91 may be performed. Depressed keys " 9 " and " 1 " in the keyboard 1 connect corresponding writing heads 32<SP>9</SP> and 321, respectively, to appropriate contacts of a denomination selector switch 40 which rotates in synchronism with the magnetizable disc 7. Thus, digit signals sensed from the left-hand track a cause corresponding signals to be recorded in the righthand track b displaced by amounts corresponding with the respective digits entered in the keyboard. Carry-over.-In the above example, the result of adding the tens digits was to record " 11 " in the tens sector of the right-hand track b. In order to correct this by entering " 1 " in the hundreds sector and diminishing the recording in the tens sector to " 1," two further tracks c and d, Fig. 10b, having non-magnetizable portions (shown cross-hatched) are employed. By this arrangement the digit signal read from the track b by the head 33 will only be recorded on track c if it is less than ten, and will only be recorded on the track d if it is more than ten. In the present example the value eleven is recorded on the track d and is then picked up by a head 37, Fig. 11b, in an arrangement which causes a reduction by ten; i.e. the remainder " 1 " is recorded on a further track e, and also the firing of a gas discharge tube 52 changes over a switch 47 so that the digit in the next higher denomination will pass from track b, Fig. 10b, via the head 35<SP>1</SP> to track c, or via the head 35<SP>2</SP> to track d, and will therefore be increased in value by unity. It will be seen in Fig. 11b that a digit recorded in the magnetizable portion of track c (and therefore having a value less than ten) is transferred to the track e unchanged. On further rotation of the disc, erasing heads 61-64, Fig. 13, remove the signals from tracks a, b, c and d, leaving the result of the computation on track e. Subsequently, these signals may be transferred back to track a for further processing or to one of the tracks f1 ... fn, or to the output means. Subtraction.-The selectable recording heads 32<SP>0</SP> ... 32<SP>9</SP>, Figs. 9a and 9b, may be provided with a second series of windings (Figs. 12a and 12b, not shown) selectable by a two-way switch to provide for subtraction by adding tens complements. " Fugitive-one " correction may be done as a separate addition operation by the carry-over means as described above or by change of digit value position during transfer from track e to track a. Multiplication.-This may be effected by a denominational displacement and, within each denomination, a repeated addition. The multiplicand digits are entered by a keyboard M, Fig. 24a, which effects connection between vertical denominational lines 151... 15<SP>8</SP> and horizontal digit-value lines 16<SP>0</SP> ... 16<SP>9</SP> (the number " 28 " is set up in the drawing). The multiplier is entered by a second keyboard 162 (which is shown with " 69 " entered). Inductors 82<SP>1</SP> ... 82<SP>8</SP> represent a series of windings, each on one arm of a U-shaped core whose other winding carries an energizing current and arranged circumferentially round a toothed member, Fig. 25a, which rotates in synchronism with the magnetizable disc so that when a tooth passes a U-shaped member the inductive coupling between the windings is so increased that a surge of voltage sufficient to prime the associated tube 88<SP>1</SP> ... 88<SP>8</SP> is developed across each winding 82<SP>1</SP> ... 82<SP>8</SP> as its corresponding sector passes under the reading head 31. When a digit signal in track a is picked up by a head 31<SP>9</SP> (cf. head 31, Fig. 9a), the signal is amplified by a pentode 74 and fires a gas tube 73 which raises the screen grid of a pentode 67 sufficiently to allow a clock pulse at its control grid to cause a second gas tube 68 to be fired and this raises the voltage on the control grid of a pentode 87 to allow momentary current through the primed gas tube 88<SP>1</SP> ... 888 and, via the keyboard contact, through the corresponding writing head 32<SP>0</SP> ... 32<SP>9</SP>. Thus, after each of the gas tubes 88<SP>1</SP> ... 88<SP>8</SP> have been fired in turn during one rotation of the magnetic disc, the value of the multiplicand is recorded in track a of the disc. (In the example shown 0+28=28.) During the second and subsequent rotations the multiplicand is repeatedly added to the previous result (28+28= 56; 56+28=84, &c.). The circumferentiallyarranged U-shaped members (mentioned above), influenced by a tooth of a rotating member, Fig. 25a, are movable as a unit axially in steps so that they can be brought into co-operation with successive teeth staggered by angles corresponding to successive denominations or sectors of the disc. Thus the effect of a column shift is obtained after each ten rotations. Instead of such mechanical displacement electric switching arrangements may be employed. In order to make effective, in each cycle of ten, the number of adding cycles corresponding to the multiplier digit for that position two rotary switches 131 and 135, stepping in a counterclockwise direction, control the current through two windings of a relay 139 in accordance with the number set up in the multiplier keyboard 162 (" 69 " in the example). Each step of the switch 131 corresponds with a rotation of the magnetic disc, and a complete rotation of switch 131 corresponds with one step of the switch 135. Each time switch 131 comes to the zero position with its moving arm on contact 133<SP>0</SP> a circuit is completed from the positive supply, through winding 139a of a relay 139, through the switch 131 and a second winding 139b of the relay. When both windings are energized contacts 140, controlled by this relay, remain closed and adding operations are effective; when, however, a circuit exists from the positive supply via switch 135, a keyboard contact, switch 131 and winding 139b only, contacts 140 open to render further adding cycles ineffective. When the keyboard contact is in the zero position the winding 139a is short-circuited. Division differs from multiplication only in that, after the entry of the dividend by a single addition, repeated subtraction of the divisor by complementary addition is performed until the remainder becomes negative as indicated by the absence of the " fugitive one " ; the remaining subtractions are rendered ineffective and during the tenth cycle an addition is made to make the remainder positive before the " shift " is carried out and the process is repeated. Other embodiments including alternative arrangements and simplifications are described. For example, in Fig. 35, the elements 126<SP>0</SP>, 126<SP>1</SP>, 126<SP>2</SP> ... &c. represent the staggered teeth of a rotating member surrounded by pairs of windings 240, 250; 241, 251a, &c. on U-shaped cores which are momentarily bridged by the passage of a tooth across the gap. One digit is entered via sensing head 31<SP>1</SP> or 31<SP>2</SP>, switch 47 (cf. Fig. 10b) and amplifier 67, in the form of a timed pulse which fires a gas tube 237 at a time in the cycle corresponding to the digit value. A corresponding pulse is transmitted by the presence of the tooth 126<SP>0</SP>, to the secondary winding 239<SP>0</SP> ... 239<SP>9</SP> of that digit value and fires an associated gas tube 244<SP>0</SP> ... 244<SP>9</SP>. This selects one of the columns of primary windings 240, 241, 242 ... &c. in accordance with the value of the first digit; the second digit entering into the computation, is set up in a keyboard 1 and selected as to its denomination by a stepping switch 42. Thus a circuit is established for one only of the primary windings, and when the appropriate tooth 126<SP>0</SP> ... 126<SP>9</SP> passes, a timed pulse representing