Apple Express Fax/Modem - Manual (Page 144)

&Q n Connection mode This command allows you to enable and disable
error control mode. The &Q command setting has precedence over
\N command setting and registers S36 and S48.
0 Asynchronous mode (no error control, disables V.42 and MNP).
5 Error control mode Instructs the modem to make a connection
using V.42/MNP, and fallback as necessary (see S36 and S48
registers).
&R n CTS/RTS Since bus modems have no DTE-DCE serial interface, this
command has no effect and remains for scripting compatibility.
0–1 Return OK.
&S n DSR Since bus modems have no DTE-DCE serial interface, this
command has no effect and remains for scripting compatibility.
0–2 Return OK.
&T n Self-tests The following diagnostic tests are provided. These tests are
available only when no error protocol is engaged. The duration of each
test is controlled by register S18.
0 Terminate the test Used to terminate (escape from) a test in
progress and return to command state, if S18=0.
1 Local analog loopback Initiates a local analog loopback test. The
escape sequence must be entered to terminate this test. This mode
tests the local modem and the local data terminal equipment.
3 Local digital loopback Initiates a local digital loopback test. The
modem echoes characters back to the remote modem exactly as
received.
4 Enable the remote digital loopback Enables the modem to
respond to a remote modem attempting to place it in digital
loopback test. If a remote modem places the local modem in
remote digital loopback mode, the local modem echoes characters
back to the remote modem exactly as received from the remote
modem.
5 Disable the remote digital loopback Prevents the modem from
responding to a remote modem attempting to place it in the digital
loopback mode.
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