Were the above networks truly "private", that is, owned, maintained, and operated by the corporations? Since you could dial into them from the outside, it sounds like they were Bell provided "SCAN" networks. I forgot what SCAN stands for, but many very large corporations had (have) them to interconnect different locations. It was basically a sophisticated network of WATS, tie-lines, and FX lines*. A telephone would have two numbers on the number card, one the regular Bell number and one the SCAN number. To use SCAN, users typically dialed 8 (or another access code), then the SCAN number. On some systems, you could get an outside line in a distant city to avoid toll charges. They are still in use today.
The outside access was to allow employees, such as salesman, to call in and connect anywhere without toll charges.
Years ago employees of such companies would love such systems because it enabled them to call friends/relatives in distant cities without toll charges. The corporation might not be paying for an individual call, but it did have to pay for the tie-lines and heavy personal use meant it had to add more very expensive WATS or tie- or FX lines.
- A tie-line is a trunk that interconnects two separate PBX systems. A "FX" foreign exchange is a telephone line that is served by a distant city. This enables callers to reach a company via a local call and a company to call that distant place without toll charges. An example of use is major resorts having reservation lines to big cities. For example, Catskill resorts would have tie lines to New York City, Pocono resorts would have tie lines to Philadelphia. On the switchboard tie lines had special heavy wire since they had higher line voltage to accomodate the distance.
Also, many suburban businesses and residences had FX to a city exchange to avoid paying message unit charges in both directions. For businesses this is a consideration.
[TELECOM Digest Editor's Note: Although Stanotel was always closely guarded against outside intrusion, the only reason Unitel was wide open was due to stupidity; the manager of same did not know how to block any sort of intrusion. One of the first things I did after learning about Unitel was verify the local Elk Grove numbers. Using the old, stale trick of dialing a 'local' (9-level) call as a zero plus call to the Waldorf-Astoria hotel in New York City person to person to Mr. Smith, I asked my operator to leave word if Mr. Smith had not yet checked in. "Surely," she responded, and told the Waldorf- Astoria operator to leave word for Mr. Smith, asking 'him' to call Operator 7 in Chicago and that the number calling was (whatever). Had I simply dialed the operator and asked what my number was, I would have been told I should know my own number, and refused any further information. _Thank you_, operator. Two or three months later, I discovered the inbound number for Unitel was no longer getting answered, so on a hunch I dialed the formerly _outbound_ number, and as I suspected, it was answered by dial tone. The only thing the foolish people had done was swap the two numbers in the plug-in call-extender device. That was _their_ notion of what security was all about (this was the 1980's). So, Lisa, strictly speaking, Unitel nor Stanotel were intended for 'public' use.A third example of this was Chicago, Nilwaukee and Northwestern Railroad which had a large office in Chicago, wherein they had a Dimension PBX. No one from telco ever bothered to explain to any railroad employees that Dimension always had a remote port on it for 'testing and repair' purposes, with its own distinct phone number on that line. Nor did they ever explain that the passcode on such systems was factory-defaulted to four zeros, i.e. '0000'. The rail- road found out the hard way on that; a phone bill one month in the thousands of dollars. The last thing I heard (late 1970's) two Illinois Bell Security guys were roaming around up in Minnesota trying to track down recipients of phone calls. PAT]