Answering From Synchronous Mode; Auto-Answer; Manual Answer - ZyXEL Communications U-336S User Manual

Once the modem is connected, the modem will enter synchronous
operation.
2. Dial through the computer using V.25bis commands: Some
communication software packages on synchronous computers can
dial using V.25bis synchronous commands. In this case, set &M3
and *I1 and the modem will accept V.25bis commands and make a
synchronous connection.
3. Using DTR to dial a stored number in synchronous mode :
Store the telephone number by the asynchronous command &Zn=.
Use the DEFAULT DIAL parameter menu or *Dn command to
select the default dial pointer. Set &D1 and either &M1 or &M3,
then raise DTR from your terminal or communication software. The
modem will dial the default stored number. After the modem is
connected, the modem will enter synchronous operation.
4. Manual dial: Set the modem to synchronous mode (&M1 or
&M3), then dial a number from a telephone set. When you hear the
answer tone, type ATD (if &M1 is set). The modem will go into
synchronous operation after connection.

Answering from Synchronous Mode

Auto-Answer

Set the modem to synchronous mode. Set the S-register S0 to equal the
number of rings before auto-answer occurs. Set it from the terminal (if
&M1 is set) using the asynchronous AT command, or select the
STATUS REGISTER menu to change the S0 value.

Manual Answer

Type ATA from the terminal (if &M1 is set) or press "A" in the idle
screen of the LCD panel.
LCD Panel Operation 45