ZyXEL Communications Prestige 623ME-T User Manual page 246

Prestige 623ME-T 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.
F-2
Diagram F-2 Connecting a Microfilter
Splitters and Microfilters