ZyXEL Communications PRESTIGE 652H User Manual page 504

Prestige 652 Series User's Guide
Step 2.
Connect a cable from the double jack end of the Y-Connector to the "wall side" of the microfilter.
Step 3. Connect another cable from the double jack end of the Y-Connector to the Prestige.
Step 4. Connect the "phone side" of the microfilter to your telephone as shown in the following figure.
Prestige With ISDN
This section relates to people who use their Prestige with ADSL over ISDN (digital telephone service) only.
The following is an example installation for the Prestige with ISDN.
I-2
Diagram I-2 Connecting a Microfilter
Diagram I-3 Prestige with ISDN
Splitters and Microfilters