The short-short of it: citing http://www.bitsavers.org/pdf/att/000-111_ATT_Documentation_Guide_Nov87.pdf Dataphone is a registered trademark of AT&T I saw the Dataphone label on all sorts of modems: SDLC, async, dialup and probably leased line as well. Citing Justin Jernigan's posting

It was a Service, appears to still be, though likely no longer actively sold. It's one of the first digital services tariffed by the telephone companies ... This was pre-divestiture, so service and equipment were "one"

Set the wayback machine to 1976 (the US Bicentennial). "Ma Bell" was a regulated monopoly, personified in many ways, most memorably Lily Tomlin's character Ernestine the switchboard operator. https://en.wikipedia.org/wiki/Lily_Tomlin But internally, Bell System folks were extremely proud of their work, creating and maintaining "the best phone service in the world". You were not allowed to own phone equipment: it was all leased thus all the Western Electric phones saying "not for sale". Add an extension phone and you'd get a "service call" to force you to disconnect it. Even after-market equipment was forbidden, such as the "name caller" auto-dialer (which pulse-dialed numbers you filled onto a plastic belt with an electrographic pencil). New York City high schools all had an IBM RJE (remote job entry) terminal: card reader and line printer, to a modem the operator had to manually dial with a rotary phone (no smart modems, yet!). At the other end was an IBM 360/370 running HASP or JES for batch jobs. As to the rack of modems the Original Poster remembers: that's probably intended for the receiving end: answer-only or answer-mostly mode. UUCP was the only way I was aware of AT&T hardware weirdness where the dialer was separate from the modem. -- jeff jonas