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# Sneak Path Computation

IP.com Disclosure Number: IPCOM000088548D
Original Publication Date: 1977-Jun-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 14K

IBM

Roth, JP: AUTHOR

## Abstract

The design of relay and electronic switching networks is a common feature of switching systems as a means of control, etc. Relay devices or their electronic equivalent are interconnected to form graphs. Under certain conditions on the variables controlling the state of the switches, it is desired that there be a closed path between two nodes of the graph designated as external leads. Under other conditions, it is desired that there be no closed path between this external-lead pair. A SNEAK PATH is the existence of a closed path between an external-lead pair when it is not desired that there be such. There is also the dual problem of the nonexistence of a closed path when one is desired.

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Sneak Path Computation

The design of relay and electronic switching networks is a common feature of switching systems as a means of control, etc. Relay devices or their electronic equivalent are interconnected to form graphs. Under certain conditions on the variables controlling the state of the switches, it is desired that there be a closed path between two nodes of the graph designated as external leads. Under other conditions, it is desired that there be no closed path between this external-lead pair. A SNEAK PATH is the existence of a closed path between an external-lead pair when it is not desired that there be such. There is also the dual problem of the nonexistence of a closed path when one is desired.

A method is disclosed for determining the existence of sneak paths and their duals. It assumes both a specification of the required open and closed paths, in the form of disjoint covers, as well as a description of the relay or electronic network. The logic of the network is converted into AND OR NOT logic, and then converted by means of the Pistar algorithm into ON OFF ARRAYS. These arrays are interfaced with the OFF and ON ARRAYS, respectively, of the specification. Any element in the interface or intersection, interpreted as an input pattern, would then represent a sneak path or its dual. The theorem is that a sneak path exists if and only if a term exists in the interface. THE METHOD

1. The first step consists in constructing for each pair of external leads the subnetwork or nodes and paths that connect these, and only such nodes and paths.

It is assumed that the equivalent logical network is given by a list, each entry of which consists of an output variable, the name of the function being performed, AND, OR, or NOT, together with the names of the input variables. The method of constructing the subnetwork connecting two external lead pairs consists in starting out from the nodes that connect to one external lead, finding the names of the varia...