Instead of individual batteries, one at each telephone, a large common battery was installed in the exchange itself.
This meant better signalling and better talking.

It reduced the cost of batteries and put them in charge of experts.

It established uniformity.
It introduced the federal idea into the mechanism of a telephone system.
Best of all, it saved FOUR SECONDS ON EVERY CALL.

The first of these centralizing switchboards was put in place at Philadelphia; and other cities followed suit as fast as they could afford the expense of rebuilding.

Since then, there have come some switchboards that are wholly automatic.