Apple Express Fax/Modem - Manual (Page 137)

S12 Escape code guard time
50 20:255 1/50 second
This value determines the length of time to wait for typing commands
before and after issuing the escape sequence.
S18 Self-test duration
0 0:255 Seconds
The S18 register determines the duration of the AT&T diagnostic
self-tests. If a non-zero value is chosen, the modem automatically halts
the test after the time period specified and returns to command state.
You must then issue an AT&T0 to actually exit the test. If S18 is zero,
the self-test continues until it is ended by issuing the escape sequence
to return to command mode followed by AT&T0.
S36 Negotiation failure treatment
5 0/3/4/5 Settings
Specifies action that should be taken when an attempt to connect in
error-control mode fails.
0 Attempts V.42 connection. Hangs up if remote modem does not
support V.42.
3 Makes asynchronous connection. No error control. Same as
AT&Q0.
4 Attempts V.42 connection. If attempt fails, attempts MNP 2–4
connection. If this fails, hangs up.
5 Attempts V.42 connection. If attempt fails, attempts MNP 2–4
connection. If this fails, attempts asynchronous connection.
125 M O D E M C O M M A N D S E T