Great.. finally. i manage find from solution from user guide.. L is Locked. below is the instruction. will check out tonight.
The locking function holds the current settings, or prevents anyone from starting the hob. It is also used for cleaning the control strip as the controls can be locked without the hob being on.
To lock the hob : -Press the on/off button . -Press simultaneously " - " button and " + " button of the front right zone (PVD 633 front left zone), and then press again on the " + " button of this zone. The hob is locked, the locking indicator " L " is displayed on all zones for 20 seconds.
To unlock the hob : -Press the on/off button . The locking indicator " L " is displayed on all zones.
-Press simultaneously the " - " button and the " + " button of the front right zone (PVD 633 front left zone), and then press again on the " - " button of this zone. The hob is unlocked.
Yuva
October 2008