[TriLUG] modem-to-modem connections, perle STS16

[Dewey Hylton]

hi all! i've been using modems since the early 80's when i ran a BBS, and on through the 90's
when connecting serial devices between hospitals and such. i haven't used them much at all
since 2000, and am now failing miserably to do something i believe should be extremely simple.
so i'm hoping someone here can show me what i'm missing.

i have a stack of perle devices - model STS16 - at various remote sites. the plan is to be
able to dial into a modem attached to one of the perle serial ports in order to reach other
serial devices attached to the same perle device. the perle is setup in such a way that any
connection presents a login prompt, after which the successfully authenticated user is presented
with a menu of serial ports to which they have access. this works via ssh. this also works via
direct serial attachment (using a standard cat5 cable and perle's own serial converter).

so in theory, all i need to do is to extend the serial connection across a modem-to-modem
connection. i connect one modem to each the computer and the perle device, and connect both
to phone lines. i setup the perle modem to auto-answer, and i dial to connect the two modems
over the phone line. they connect. i get nothing on the remote terminal screen. i can put the
modem into and out of command mode using the standard hayes at command set. but nothing i do
results in the appearance of the login prompt. disconnect the modems, reconnect the serial
cable, and i get the login prompt.

both modems are set to factory defaults, and both are USR Sportsters.

what am i missing?