Abstract: A method for recognizing and releasing unnecessary trunk lines in a private branch exchange telephone system including a plurality of switching nodes, each having a unique node identification number where each pair of nodes is connected by a plurality of trunk lines, includes steps for (a) compiling a telephone call identifier list containing node identification numbers and an associated trunk call identification number used in defining and connecting a call path between a calling party and a called party, (b) examining a call identifier list at each of the switching nodes for information indicative of redundant node identification numbers, and (c) releasing the unnecessary trunk lines between the redundant node identification numbers.

Abstract: A method for combining signals for a telephone conference may include a multiplicity of identical adders for combining six signals and providing a single combined output. The adders may be arranged in a repeatable hierarchical scheme in which each group of six conference members includes an adder for combining all six signals, with the output of this adder being provided to other groups of six so that each conference member receives signals from every other conference member. As few as three hierarchical levels of addition may be used with up to 216 members. Adders may also be arranged so that a member of a first conference may monitor other conferences without affecting the first conference.