What are the Call routers
Call routers A, B, C, D, and E. There are ten potential lines: AB, AC, AD, AE, BC, BD, BE, CD, CE, and DE. Each of these lines has four possibilities (i.e. three speeds or no line), so the total number of topologies is 410 equal to 1,048,576.
At 100 ms each, it takes 104,857.6 sec or somewhat more than 29 hours to inspect them all.