B737-300 CREW DSNDED BELOW THE CHARTED ALT RESTR ON THE DYLIN 1 INTO EWR.

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FLYING TO EWR; I WAS GIVEN CLRNC FOR THE PROFILE DSCNT (THE DYLIN 1 ARR). EVEN THOUGH I HAD SEEN THIS TYPE PROFILE YRS AGO FLYING INTO LAX; THIS IS THE FIRST ONE I HAD ACTUALLY FLOWN IN QUITE SOME TIME. I PUT 8000 FT IN THE ALT WINDOW WHICH IS THE RESTR AT DYLIN. AT THE TIME; WE WERE SW OF DUPONT. AT THE TIME THE CLRNC WAS RECEIVED; WE WERE AT FL250. AS I CUSTOMARILY DO; I SELECTED THE DSCNT PAGE ON THE FMC TO MONITOR THE VERT SPD REQUIRED TO MEET ANY ALT RESTR. AS OPPOSED TO WAITING FOR AN IDLE DSCNT; I NORMALLY WILL INITIATE THE DSCNT PRIOR TO THE VERT SPD REQUIRING 2000 FPM BY SELECTING THE CAPTURE MODE. THIS MODE SELECTS 1000 FPM DSCNT UNTIL THE ACFT INTERCEPTS AN IDLE DSCNT GLIDE PATH WHERE UPON THE THRUST LEVERS RETARD TO IDLE AND THE AUTOPLT INITIATES THE IDLE DSCNT. AFTER ACCOMPLISHING THIS TASK; I STARTED TO BRIEF THE APCH TO RWY 9L IN ACCORDANCE WITH COMPANY POLICY. MY ATTN WAS DIVERTED WHILE DOING SO; AND I DID NOT REALIZE THAT THE ACFT HAD DSNDED BELOW THE AT OR ABOVE RESTR AT DQO WHICH WAS FL220. APCHING FL210; THE VNAV MODE DISENGAGED GIVING A WARNING LIGHT WHICH DREW THE CAPT'S ATTN AND WE DISCOVERED THE DEV. I IMMEDIATELY STOPPED THE DSCNT MANUALLY AND CORRECTED TO ALT. WE WERE PROBABLY 4-5 DME SW OF DQO AT THE TIME. INITIALLY; BOTH THE CAPT AND I WERE UNSURE WITH WHY THE AUTOMATION; WITH THE RESTRS ENTERED INTO THE FMC; DID NOT COMPLY WITH THE PROFILE DSCNT. THE MORE I THOUGHT ABOUT IT; THE MORE I REALIZED IF I HAD LET THE ACFT DSND AT THE SELECTED IDLE DSCNT POINT INSTEAD OF USING THE CAPTURE MODE; THE PROB WOULD HAVE BEEN AVOIDED. IN ADDITION; WITH A PROFILE DSCNT CLRNC BEING SOMEWHAT OUT OF THE ORDINARY FOR ME; I SHOULD NOT HAVE ALLOWED MYSELF TO BE DISTR BRIEFING THE APCH WITHOUT ENSURING THE AUTOMATION WAS ACTUALLY COMPLYING WITH THE PUBLISHED ALT RESTR ON THE ARR. I ADMITTEDLY WAS PROBABLY TOO COMPLACENT FEELING COMFORTABLE WITH THE FMC AND DOING SOMETHING I NORMALLY DO ON DSCNTS WITHOUT CONSIDERING HOW THIS ONE WAS A LITTLE DIFFERENT FROM WHAT I HAVE BEEN ACCUSTOMED TO.