[TELECOM Digest Editor's Note: Traditional Bell had a habit of
> always using an 'X' to mean 'e(X)change', as in PBX (P)rivate
> (B)ranch e(X)change, FX as in (F)oreign E(X)change, and PAX as
> (P)rivate (A)utomatic e(X)change. An exception was FAX as in
> (FACS)imile Service. But you asked about EAX which was (E)lectronic
> (A)utomatic e(X)change, or another name for an electronic and
> automated switchboard. Of course there is also CENTREX or a
> (C)entral Office e(X)change. The only difference between a PBX and a
> PAX is the former involved an operator at a manual cordboard in a
> company and the latter was the same thing but an 'automated
> switchboard'. ...
There was also "NNX" which internally meant exchange. For the longest time nobody could tell me where that term came from. Finally I learned it was because N was 2 thru 9 and X was 1 thru 0. Of course that is obsolete now since exchanges are NXX these days. Then of course the big city exchange building that I had my tour in and learned this stuff is now abandoned and empty. Where the switchgear that served 40,000 lines is, the service center (for repair calls) and the TSP operators moved to I have no idea.
It appears Bell called all customer exchanges "PBX" whether they were dial or manual. I have a 556 (cordboard for a dial PBX) manual and it refers to the system as a PBX. The term "PABX" (private automated branch exchange" seems to more used by Automatic Electric and the independents. The private Philadelphia city goverment system even had that named labeled right on the dial card "city automated exchange". (Supposedly modern signs for phones to this day at the airport still say this, but I can't visit the airport to check and certainly couldn't take pictures on account of security. When I was young people were welcome to visit the airport and they even had a rooftop observatory.) Anyway, I suspect the use of the word "automatic" was sort of a marketing ploy by Automatic Electric Co to push that they sold dial systems over Bell's manual systems.
I wonder where the biggest non-Bell private system was. These could be pretty complex with multiple locations and tie-lines and thousands of stations.
(At risk of duplicating past posts): When the suburban NJ Lindenwold High Speed train (PATCO) opened in 1969, they installed a separate private telephone exchange for internal use just as rail lines had done for years. They picked up a used step-by-step switch. They had a tie trunk into the Phila transit private system. For passengers, they had second-hand pay phones, painted red, at stations who needed assistance with the automatic gates. If the psgr owed money, they'd put it in the pay phone. While they modernized the phones and gear, the system remains in use to this day.
A brand new line, the NJT River Line, uses an intercom phone. You press a button and an automatic dialer connects you to their service desk. Sometimes you get a busy signal, no answer, or a voice mail, which isn't very helpful to a psgr on a platform who needs help. The intercom is very hard to hear on open platforms. They also put at least one pay phone on every platform. I believe these were installed to mostly serve as 911 stations in case of emergency although there are no signs indicating such. Photos are forbidden there as well.
[TELECOM Digest Editor's Note: I do know that in Chicago in years past, Illinois Bell's largest customer was the City of Chicago itself, and its two largest _private_ (non-government) customers were the University of Chicago (19 position switchboard in three 'ranks' or position groups) and Standard Oil (a 'mere' ten or twelve position board but with a _huge_ number of private tie lines to various corporate locations plus a few hundred thousand dollars per month in long distance traffic, etc). Outside the city limits but served by Illinois Bell there were United Airlines and its Unitel network and the federal government with its Autovon network. PAT]