I was curious about the workings of private line service in the days
I understand back in the 1950s if one had private line service they
could put their own gear on it. For example, IBM pioneered with some
modems in the 1950s and used them on some private line networks.
However, they stopped quite short of trying such modems on switched
lines because (1) it wasn't allowed (2) they didn't want to upset the
phone company who was a big customer.
Why was it ok to use private gear on private lines?
I assume for long hauls, a private line wasn't a continuous physical
piece of copper wire, but a path set aside on a carrier channel of
coax or microwave. Obviously gear had to meet certain specs to avoid
harming the network.*
Also, Western Union provided private line services, including voice
and broadband, in competition with AT&T. W.U. attempted to offer a
voice service but I don't think it had too many customers.
Could anyone set up a private line between two fixed destinations
under contract? For example, suppose I somehow managed to have a wire
running 100 miles. The Jones Co. wanted a line between its HQ and a
branch and my wire directly served both locations. Could I offer that
service to Jones, or was that restricted to registered and regulated
common carriers (like AT&T and W.U.)?
When MCI broke into the Bell monopoly in the midwest, was it offering
a direct physical connection point to point, or was it demanding
interconnection via Bell System lines to the final destination?
Any information on the policies and workings of private line services
would be appreciated. [public replies, please]
* As to the issue of harming the network, some of the things the
regulators and companies were concerned were a faulty gear constantly
requesting line service or causing disconnects which wouldn't be an
issue on a private line. Also, regulators deliberated charged more
for equipment to offset the cost of very basic service so that more
people could afford entry level phone service. In other words, an
intentional cross subsidy.
[TELECOM Digest Editor's Note: Although what you say is correct, telco
had very strict rules on things. For example, a pair of wires from
point A to point B which did not go near an 'actual phone line' but
was still used for communication purposes was regulated according to
Bell rules and defined as a 'private line' according to their
rules. The Harper Theatre in Chicago (legitimate playhouse), in
addition to its 'regular' phone line, BUTterfield-1717 had a totally
uninvolved wire pair loop which ran from one side of backstage to the
other side of backstage, then to the lighting and sound booth, and the
first floor ticket office. They installed it privately. The intent was
for those employees to be able to communicate with each other in the
course of a play in progress. No switching equipment on it, no telecom
gear in use except maybe a couple of operator headsets and a
speakerphone somewhere. It all ran with a little independent power
supply. Illinois Bell kept insisting they wanted in on it ... it was a
'private line' by their standards, and they (telco) were the only
people authorized to provide that communication service. Harper
Theatre finally gave in on it and started paying Bell some fee each
month (for nothing, except the right to not be blackmailed by
Bell).But the theatre insisted in return to be allowed to use a 'two
line, twist button' style phone with the 'private line' terminated on
one side of the twist in exchange for the money they were forced to
pay. Telco finally assigned it a 'Private Line Circuit Number.' PAT]