Re: Very Early Modems

> The passage said that AT&T strictly controlled attachments

> to their lines; the IBM system was used mostly on private lines or > leased lines. As we recall, many large organizations, especially > railroads, >>maintained their own privately built and maintained > telephone networks and such users could of course attach anything > they wanted. Railroads could use this IBM system to send in > freight car movements punched at remote locations to a central > site. Railroads (and other "right-of-way" companies) could use > their lines as they saw fit, including imterconnecting with Bell > lines at their PBX (including dial PBXs). This was true whether the > company owned the lines or leased them from Bell. > But I wonder if AT&T allowed private attachments to leased private > lines it supplied. I wonder if the rules were different for such > lines as opposed to the switched network. I also wonder if the > independent telephone companies were as strict as AT&T regarding > attachments. The rules were indeed different on private lines. > Generally the customer could hang anything they wanted on leased > lines as long as they did not cause interference outside the > bandwith. (Leased lines included telegraph, teletypewriter, voice, > program channels [audio channels with wider bandwith than > voice-grade channels], television channels, and various grades of > data channels.) Most independent companies were even more > restrictive than Bell in their regulations, both for lines attached > to the switched network and for leased lines. > Wes Leatherock >

I also had several earler modems predating 300 baud. These operated at

110 baud, 75 baud, and 56 baud. The slowest of the modems were used with circuits where data was badot and tty codes.

- Steve Hathaway

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Steven J. Hathaway
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