. The Bell System technical journal . l selector switches most generally areset progressively. In systems with relays or relay-like crosspoints allcrosspoints involved in a connection may be actuated either case the switching device, or the circuit in which it is used,has a form of memory. This memory, shown as a square labeled M inFig. 4, may be the ability of a selector to remain mechanically held in aparticular path connecting position or in a locking or holding circuitassociated with a crosspoint relay or crossbar switch magnet. To minimize the time consumed by the common
. The Bell System technical journal . l selector switches most generally areset progressively. In systems with relays or relay-like crosspoints allcrosspoints involved in a connection may be actuated either case the switching device, or the circuit in which it is used,has a form of memory. This memory, shown as a square labeled M inFig. 4, may be the ability of a selector to remain mechanically held in aparticular path connecting position or in a locking or holding circuitassociated with a crosspoint relay or crossbar switch magnet. To minimize the time consumed by the common control elements,simultaneous operation of relay or relay-like crosspoints is most de-sirable. However, this type of network requires a grid of link testingand control leads such as shown in Fig. 5 for a typical stage of a cross-bar switching network. In a network of this type the calling rate ca-pacity is limited by the slow actuating speed of the electromechanicalrelay or switch. Efficient network configurations can be devised for. Fig. 3 — Tone ringer telephone set. 996 THE BELL SYSTEM TECHXICAL JOURNAL, SEPTEMBER 1956 large capacity. To set up connections at a high rate in such a networkrequires a pluraHty of controls each capable of operating on all or partof the network. In any case, the controls function in parallel on thenetwork because of the speed considerations. With electronics applied to space division switching networks, twoimprovements over the operation of relay type space division networksmay be achieved. First, the speed of operation of the crosspoint elementsmay be made high enough so that only one control is needed to operateon networks of the size now requiring a plurality of controls. Second,the properties of proposed electronic crosspoint elements are such thatthe principle of end-marking may be employed. In contrast to the grid of testing and actuating wires required inelectromechanical versions of space division networks, the electronicspace division
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