Patent GB-1160594-A (GB)
Title: Simulating apparatus for use in Critical Path Analysis
Inventor: ETTINGER GEORGE MICHAEL
IPC: G06G7/122
Filed: 1966-12-21
Abstract: 11,60,594. Operational simulating apparatus. G. M. ETTINGER. 10 Jan., 1968 [21 Dec., 1965], No. 57265/66. Heading G4G. An electric analogue network simulates critical path analysis of a project, wherein nodes of a diagram (Fig. 1, not shown) represent stages of the project and are conjoined by arrowed paths designating activities; each of which is allotted an estimated time and the total project time depends on the time of the longest irreducible sequence of events derived by following all possible permissible paths. A panel 20 (Fig. 2) carries plural units 41 each comprising a D.C. source controlled by potentiometer and dial 21, 22 to develop voltages representing the various activity times across terminals 23, 24 which may be patched by leads and plugs to other such terminals or to input and output terminals 31, 34. Each unit also comprises a neon lamp 25, an inscription panel 26 for the relevant activity, and a socket and terminal 27, 28 receiving a node unit (Fig. 4). Input terminals 31 are commoned to switch 29 to be earthed in START position and connected to terminal 30 in CARRY position for interconnection to other networks. Output terminals 34 are connected to FINISH/CARRY terminal 35 connectible to the CARRY terminal of another network or to a voltmeter 36 shunted by a standing D.C. source 39, 40 and standing A.C. source 37, 38; arranged to measure the voltage between input and output as a measure of the critical path length. Each D.C. source (Fig. 3) comprises a transformer 47 switchably energized across A.C. source 50 with a pilot lamp, to energize a stabilized rectifier connected to the split windings of transformer 45 separated by the control potentiometer; terminals 23, 24 being connected to the end of one winding and to the slider. Series secondary windings energize the emitter/base of transistor 46 to switch on neon indicator 25 when an A.C. signal appears in the secondary; the transformer being such that the primary D.C. produces no net flux while A.C. signals between 23, 24 induce secondary adding signals. A nodal circuit unit (Fig. 4) comprises diodes 55, 56, 57 whose anodes are patched to terminals 24 of corresponding units 41, while the common cathode is patched to terminals 23 or 34, and resistor 58 is connected to standing negative source over terminal 28 when the unit is plugged into socket 27; the terminal 62 thus assumes the highest or most positive potential of those applied to terminals 59, 60, 61 which opens the appropriate diode, so that in a complete network the potential magnitudes are proportional to the times of the corresponding activities, and voltmeter 36 denotes the total project time; and the open diodes are transversed by the A.C. signals from 37, 38 to illuminate the neons 25 of the D.C. sources 41 corresponding to critical path activities, so that the path is indicated. Variations of individual potentials simulating variations of activity times cause extinction and illumination of neons to denote consequential changes of control path. Calibrated increase of the A.C. source enables other paths closely approximating the centre to be indicated by illumination of the appropriate neons. An alternative D.C. source (Fig. 5, not shown) employs diodes inserted between the potentiometer slider and terminal 24, and between the end of the primary winding and terminal 23, while the nodal diode unit is eliminated. Servomotors may be employed to adjust the potentiometers in sequence to the required setting, and for the potentiometer voltages to be successively connected to measuring apparatus for recording in data storage equipment the estimated completion instant of each activity, with a printout of whether or not such activity is critical. Dials 22 may be replaced by remote numerically indicating discharge tubes.