ZyXEL Communications U-336S User Manual page 71

2. Set S51.0=1 to enable EDR and report RING twice. The
modem will not report a normal RING and ZFAX will not
answer a call unless EDR RING is reported.
3. Set S51.4=1 to enable fax CNG tone detection. It is reported as
RING.
4. Set S51.2=1 to enable DTMF tone detection. It is reported as
RING. If the remote fax machine does not generate the CNG
tone, ask a fax caller through your answering machine message
to press "*" (or any other DTMF key) if he or she wants to
send a fax.
Save the settings in a profile and reset the modem with AT&WZ.
Special Functions 59