 For example, for a switch with 1000 input customers and 1000 output customers, a traditional system able to route 1000 point-to-point connections simultaneously—in any possible permutation—would require a matrix of 1000×1000, or 1 million, physical switches for full interconnection possibility.When one considers that a large telephone system can have many more than 1000×1000 customers, the hardware to establish a full interconnection can grow rapidly and exceed practical implementations.Edson Erwin devised the Clos network in 1938 (as formalized by Charles Clos in 1952) which improved on the formula_3 bound.