Patent GB-1173796-A (GB)
Title: A Circuit Arrangement for Determining an Optimum Path
IPC: G06Q10/00
Filed: 1967-02-24
Abstract: 1,173,796. Determining optimum path; road traffic signalling. SOC. NATIONALE D'- ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. 24 Feb., 1967 [26 Feb., 1966], No. 9036/67. Headings G4A, G4P and G4Q. Problems of the optimum path type are solved using a circuit network with means for determining the shortest signal path therethrough. The network comprises node elements linked by so-called loop elements. One or more node elements are selected as arrival nodes and one or more as departure nodes, the problem being to determine the shortest path between a departure node and an arrival node, each loop element being weightable to impose a predetermined delay on signals. A clock generator applies clock pulses to all the node elements simultaneously, then all the loop elements simultaneously, then all the node elements &c. A node element can be enabled in which case the next application of a clock pulse thereto will set a bi-stable therein. A loop element can also be enabled in which case, if the element is weighted, subsequent clock pulses applied thereto will be counted (binary counter) and when a predetermined count is reached the next clock pulse applied will set a bi-stable in the loop element. If the loop element is unweighted (no counter) the first clock pulse applied after enablement will set the bi-stable. Initially all the arrival node elements, are enabled simultaneously. When the bi-stable in a node element is set it enables all loop elements (in any) fed from the node element (the loop elements are oriented in this sense, though loop elements oriented in opposite directions may be connected between any two node elements) and disables any loop elements feeding this node element. When the bistable in a loop element is set it enables, via an OR gate if necessary, the node element fed from the loop element. In this way signals progress through the network from the arrival nodes. The first departure node to have its bi-stable set terminates the above process and causes a signal to be transmitted back via the sequence of node and loop elements concerned to the particular arrival node whose initial enablement ultimately caused the setting of the bi-stable in the departure node. This transmission back, which causes the path to be displayed, can go through a given loop element only if its bi-stable is set (as it will be along the desired path) and an inhibition signal is absent. This inhibition signal can be applied to eliminate some paths (from a loop element bi-stable in the retained path) if more than one path would otherwise be displayed, i.e. a plurality of paths are equally optimum. Transmission through the node elements is immediate and unconditional, or may be blocked and delayed in bi-stables. Provision is also made for preventing the original enablement of any loop elements, to effectively remove them from the network. The network can be implemented using electronic, electromechanical, mechanical, hydraulic or pneumatic means. One application is traffic control, the node elements representing points where traffic jams are likely to occur, and the loop elements representing routes between them. The optimum path (route) determined is used to control luminous or electromechanical signals at cross-roads.