It is not any one's invention, as the telephone was.

It is a growing mechanism that is not yet finished, and may never be; but it has already evolved far enough to be one of the wonders of the electrical world.

There is probably no other part of an American city's equipment that is as sensitive and efficient as a telephone exchange.
The idea of the exchange is somewhat older than the idea of the telephone itself.

There were communication exchanges before the invention of the telephone.

Thomas B.Doolittle had one in Bridgeport, using telegraph instruments Thomas B.A.David had one in Pittsburg, using printing-telegraph machines, which required little skill to operate.