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A make-busy identified the part being worked on as in-use, causing the switching logic to route around it. A similar tool was called a TD tool. Delinquent subscribers had their service temporarily denied (TDed). This was effected by plugging a tool into the subscriber's office equipment on Crossbar systems or line group in step-by-step switches.
A double switch, or double slip—the points are set to connect the upper left and lower right tracks. A double slip switch (double slip) is a narrow-angled diagonal flat crossing of two lines combined with four pairs of points in such a way as to allow vehicles to change from one straight track to the other, alternatively to going straight ...
A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.
The Number Five Crossbar Switching System (5XB switch) is a telephone switch for telephone exchanges designed by Bell Labs and manufactured by Western Electric starting in 1947. It was used in the Bell System principally as a Class 5 telephone switch in the public switched telephone network (PSTN) until the early 1990s, when it was replaced ...
The numbers within the triangle count partitions in which a given element is the largest singleton. The number of partitions of an n-element set into exactly k (non-empty) parts is the Stirling number of the second kind S(n, k). The number of noncrossing partitions of an n-element set is the Catalan number
The switch operator has a switchboard in their tower that allows them to change the switches. [1]: xii [7]: 74 [6] Interlocking signals also tell train operators which way switches on the subway are set. The top part of an interlocking signal indicates the condition of the block ahead, while the lower part indicates the route selected.
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A set of polygons in an Euler diagram This set equals the one depicted above since both have the very same elements.. In mathematics, a set is a collection of different [1] things; [2] [3] [4] these things are called elements or members of the set and are typically mathematical objects of any kind: numbers, symbols, points in space, lines, other geometrical shapes, variables, or even other ...