Strowger phone system?

Hicken65 just replied to me on youtube, i quote: My demonstration unit was designed to demonstrate how a call progressed through a SXS switching system. Each switch can only handle one call at a time. When a switch is used on a call it is tied up to that call for the entire duration of that call and so cannot be used to process any other calls. When a call is established through my demo unit, all 7 switches are tied up for the entire duration of the call.

 So the demo unit can only have one established call at any given time. In a very large central office, each established intraoffice call would also tie up 7 switches, but there were many thousands of these switches. Each telephone line did not have its own dedicated switch or set of switches.To make efficient use of the switches, there was a great deal of shared access to them. For example, line finders were arranged in groups of up to 20 that had shared access from 200 lines..

 and connectors were arranged in groups of up to 10 that shared access to the same 100 telephone numbers. Between the line finders and connectors were the ranks of selectors. Each line finder was tied directly to its own first selector. After that, the 2nd through 5th selectors were set up to be accessed on a shared basis from the preceding rank of selectors.Typically, SXS systems were provided with sufficient switches such that 7% to 10% of the telephone lines could be in use simultaneously.