Q. Designing 100 line exchange using Uni-selector?

Here three different designing methods for 100 line exchange are discussed:

Design: Strowger switching system is designed using one two-motion selector for each subscriber. A subscriber is assigned a number in the range 00-99 and same number is used to identify two-motion selector assigned to him. 100 outlets of each two-motion selector are numbered as per the scheme given in table. Corresponding outlets in all the 100 two-motion selectors are commoned and folded back to corresponding inlets. For illustration a subscriber with 87 as his number is assigned two-motion selector 87. Outlet 87 which corresponds to this subscriber is connected to 7^th contact in the 8^th vertical position of all two-motion selectors and folded back to his inlet. Arrangement is demonstrated in figure. If subscriber 23 dials 87, his two motion selector 23 would step vertically 8 times corresponding to first digit and would step horizontally 7 times to reach contact to which the subscriber 87 is connected. This switch is non- blocking and uses only one stage of switching elements. As two-motion selector is activated by calling party, call is terminated only when the calling party disconnects the line. If a two-motion selector goes out of order, subscriber connected to it won't be able to make any outgoing calls though can receive incoming calls. Design parameters of this switch are:

S =100, SC =50, K = 1, TC =1,

EUF = 0.5, C= 200, CCI =25, P_B =0.