Jeff (aka Bags):

... There was a monitoring service offered as well (wonders just how much you can monitor a line at 2400 baud) under the same brand name.

My guess: pre-divestiture phone lines were "voice grade": not guaranteed for FAX or data, thus requiring conditioning upon install and monitoring afterwards lest you get crosstalk, static and other interference. Neil Cherry:

I used to use Paradyne 740 muxes to break those out.

Ah yes, modem sharing units. A strange kludge: some were "statistically multiplexed" to allow for different speeds, others were round-robin multiplexed, and others merely or-ed all the signals (I used those with software collision detection with per-packet ack-protocol!)

I also recall the Baby Bells delivering a special current loop line for AP News service (I think it was dry). Those were fun, 28.8 baud.

My local library had one of those teletypes clattering out the news. AT&T used to be "American Telephone and TELEGRAPH", thus the data lines! I'm unsure how they competed with Postal Telegraph and Western Union (my grandpa was a telegrapher). It was a sad day when AT&T decommissioned the last telegraph line. I remember the AT&T president saying that they'd remain "American Telephone and Telegraph" in honor of their heritage, but the following president undid that, making the name just "AT&T". Related to that: telegraph lines used to follow the railroad tracks, mostly for the railroad's internal use. Customer telegrams were sent when the lines were otherwise idle. Years later, right of way was a key part for competing phone companies: citing https://www.npr.org/2012/10/15/162963607/sprint-born-from-railroad-telephone... Sprint Born From Railroad, Telephone Businesses Melissa Block explores the long family history of the companies that comprise what became Sprint. It all began in Kansas in the late 19th century and came to include a long distance system created by the Southern Pacific Railroad Internal Network Telecommunications, or SPRINT. -- jeff jonas