[comp.sys.cbm] Analog loopback mode of a modem

prindle@nadc.nadc.navy.mil (Frank Prindle) (09/28/90)

Analog loopback is a test mode in which the modem goes into originate mode
on its send half, and answer mode on its receive half, thereby talking into
its own ear, so to speak. A properly functioning modem thus tests all of
its circuits, both analog and digital, by echoing each transmitted character
back to its received data. Not a wholly useful mode for normal operations,
it is reserved for testing a potentially defective modem.  Since AL mode will
cause the modem to drop carrier out the phone line, you generally cannot
select this mode if the modem is off-hook.
Sincerely,
Frank Prindle
Prindle@NADC.navy.mil