Patent GB-918762-A (GB)
Title: Improvements relating to electronic analogue computers
Inventor: TERRETT DAVID STUART
IPC: G06G7/06
Filed: 1958-04-28
Abstract: 918,762. Electric analogue calculating. FAIREY CO. Ltd. July 28, 1959 [April 28, 1958], No. 13473/58. Class 37. General.-An electric analogue computer comprises plural computing units interconnectible to represent an equation or equation to be solved, each comprising a D.C. amplifier and an associated function unit in which impedance components are switchable into computing networks in conjunction with the amplifier; each amplifier and each function unit being constructed in the form of a thin slab, and plural function units being mounted with their large faces parallel and a narrow edge of each exposed at the front of a computing panel with corded plug-and-socket connections on each edge and also plug-and-socket interconnecting at the rearward edges, while corresponding amplifiers are similarly mounted directly behind the function units with which they co-operate, with plug-and-socket connections at the forward edges. Assembly.-The computer (Fig. 1) is housed in racks 11 to 15 of which 13 accommodates a meter panel 18, a starting panel 19, a master control panel 20, and an automatic gain-setting instrument for coefficient potentiometers in conjunction with function units and amplifiers, while racks 11, 12, 14 each accommodate coefficient setting potentiometer panels 22 separated by computing panels 21, with a connection panel 23 having a field of sockets multipled to corresponding sockets in other connection panels and other sockets connected to outlets of the rack 13. Rack 15 accommodates servo operated potentiometric multiplication or division units 24. Computing panels.-Each panel 21 comprises a a rectangular base 30 (Fig. 2), divided by a bulkhead having front and rear walls 33, 34 and a top platform 35, with vertical partitions 36 fitted at right-angles thereto. Twelve slab. shaped function units 45 are fitted between the forward portions of the partitions and have multiple plugs 46 co-operating with corresponding sockets on front wall 33, and also plural sockets 48 on their front edges connectible by plug leads to other points of the computer. A slab-shaped computing amplifier 50 is inserted behind each function unit between the rearward portions of the partitions and has a multiple plug co-operating with a corresponding socket on rear wall 34, and a socket base for a plug in standby/compute relay 55 is mounted on. the top platform 35 between each amplifier and its function unit, while rear wall 34 can be rotated about its upper edge to expose the socket and relay base terminal wiring. Sockets 47, 52 and relay 55 are interconnected (Fig. 3) with the amplifier socket output 61 led direct to the function unit output 62 while the amplifier input 63 is connected direct to a summation contact 64 of socket 47 and to relay moving contact 66 normally closed to summation standby contact 68 and normally open to summation computing contact 69 which is also connected to contact 71. Relay control 70 is normally closed to the latter and open to contact 72 adapted to short-circuit resistor 73 in series with an A.C. fed indicator lamp 75 visible under the associated function unit, and manually-operated switch 76, which is operable to dimly illuminate the lamp and through other contacts to energize the associated relay (in series with a master switch in the central control rack) which operates to short resistance 73 and brightly illuminate the lamp. Contacts 77 of socket 47 are connected to the control rack patchboard panel as set forth over multiple cables 78. Function units.-Fig. 4 shows a summation unit for plug connection to socket 47, wherein feed-back resistor 82 is connected across the amplifier over contacts 81, 83, the amplifier output is connected to plural output sockets 84 on the front of the unit, and plural input sockets 87 thereon are connected over summation resistors to the function of contacts 67, 71 (Fig. 3) over contacts 85, 69. Inputs 87 are respectively connected directly over contacts 88 to contacts in sockets 77 (Fig. 3), and standby contact 89 earthed through resistance 90 is connected over contacts 89, 68 to contact 66 (Fig. 3). In both standby and compute conditions, the amplifier summation point is connected to one end of the feed-back resistance 82 whose other end is returned to the amplifier output and in standby condition the summation point is returned to the earthed resistance 90, and the input impedances of the function unit are earthed over contact 71. Closure of the appropriate unit switch dimly illuminates the indicator lamp, and closure of the master switch energizes the relay to brighten the lamp, disconnect the input impedances and the summation point from earth, and interconnect them for summation. Fig. 5 shows an integration unit connectible and operable similarly to the summation unit described, in which feed-back resistor 82 is replaced by integration capacitor 92. Units may be constructed to conduct other mathematical operations and may comprise a quadratic multiplying unit (Fig. 8) physically constructed to plug into the computer assembly in lieu of two normal function units. A generator 135 (Figs. 9, 10, not shown) produces triangular waveforms applied to opposite diagonals 143, 144 of a bridge circuit comprising two oppositely poled pairs of series assisting diodes 136, 137 and 138, 139, together with any number of input resistors for the pair of combined functions to be multiplied. Other diagonals 145, 146 are connected to the input and the output of feedback amplifier 147 and to the input of feed-back amplifier 148 supplying the unit output 150 over filter 149. A further input is applied to amplifier 148 over series resistor 151. It is shown that for inputs X, Y the output is proportional to (X<SP>2</SP> - Y<SP>2</SP>), and to X<SP>2</SP>, ( - Y<SP>2</SP>), for inputs (X 1 O) and (O 1 Y). For inputs (X+Y) and (X - Y) the output is proportional to XY; for inputs (y+KŒV) to 143, 144 where V is the output and input x is applied over resistor 151,   the output V is proportional to x/y ; and for inputs K,2V+K to 143, 144 and ( - x) over resistor 151 the output V is proportional to #x. A 5-way selector switch (not shown) may be provided to determine the required operation, and a sign reversing switch to interchange the connections of the diode bridge and the triangular waveform generator with regard to the remaining inputs and to exchange (x<SP>2</SP> - y<SP>2</SP>) and (Y<SP>2</SP> - X<SP>2</SP>). A unity gain sign reversal amplifier may be added if required. Coefficient setting-panels 22 each comprise twenty-four ten-turn helical potentiometers controlled by knobs 94 (Fig. 1) and earthed at one end ; the sliders and live ends being brought out to corresponding pairs of sockets 95. Computing amplifiers (Fig. 6) are drift corrected printed circuit D.C. amplifiers constructed in slab form ; each comprising a pentode longtailed pair 111, 112 with common cathode resistor 113 and input derived from terminal 114 to grid of pentode 111, followed by pushpull double triode 116 feeding half of a double triode 117 whose other half acts as a cathode follower output stage feeding terminal 118. Drift is corrected by electromagnetic vibrator 101 whose earthed moving contact 102 alternately engages contact 103 resistor-connected to the D.C. amplifier input and capacitance connected to the input of A.C. amplifier double triode 107 ; and contact 104 capacitor connected to the output thereof. Departure of the D.C. amplifier input from earth develops a square wave signal at the A.C. amplifier output which is smoothed by resistors 109 and capacitors 110 to a correction signal applied to the grid of pentode 112 of the D.C. amplifier. The computing amplifier may terminate in a cascade output stage (Fig. 7, not shown) comprising a pentode to whose grid the amplifier is connected with its cathode in series with the anode/ cathode circuit of a further pentode as load impedance; then electrodes of both valves being appropriately biased from a potential divider incorporated in the amplifier unit or assembled separately as a slab-shaped unit substituted for a function unit. Potentiometric multiplers 24 comprise (Fig. 11) plural potentiometers 171, 172, 173 &c. on a common shaft of rebalancing biphase motor 174 A.C. energized over 90 degrees phase shift 182 and modulator amplifier 181 receiving the amplified output of potentiometer 171 in combination with input X; potentiometers 172, 173 being energized by inputs Y, Z to derive outputs proportional to XY, XZ. The potentiometers are energized with voltages balanced about earth to give four quadrant operation, derived e.g. from phase-reversing amplifiers (Figs. 13, 14, not shown). Division may be achieved by supplying potentiometer 171 with input X, potentiometer 172 with Y, and potentiometer 173 with the amplified signal from the slider of potentiometer 171 ; the potentiometers being all returned to earth and an output prox portional to - derived from the slider of 172 y  through a buffer amplifier (Fig. 12, not shown). Test panel.-The outputs of all the amplifiers are connected through their plugs and sockets to a test panel of the control rack 13 comprising a uniselector sequentially scanning the outputs in standby condition to drift voltage. If such voltage exceeds a preset value, the uniselector stops and an indicator lamp shows the faulty amplifier. Patch board panel.-The function unit inputs and outputs in addition to their front socket connections are also connected through their fixed plugs and sockets to appropriate contact sockets in patch board panels 25 into which corresponding plug boards may be forcedly inserted after predetermined computing connections have been set up between selected plugs by soldering. Gain setting tool (Figs. 15 and 16, not shown) of the kind described in Specification 918,761 is incorporated in the central rack 13. Initial conditions panel.-The Pro