Historical Rules About Private Line Services?

I was curious about the workings of private line service in the days of regulation.

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]