I want to record extracts and once I reach the recording process , the lights blip and the sign ' unlock' appears ? What does it mean ??? Thank you Bruno

By 'Unlock din', do you mean unlock the region the recorder uses, unlock the din input or unlock the tray or what?
When recording and you see 'unlocked', it means the DIGITAL signal you are trying to record is unclear or missing.
If you are trying to record a signal from another region disc, it will not copy. Add a little detail.

OPC means the unit had trouble Optical Processing Calibration, which means the disc surface may be damaged. Using brand name media and being careful to not touch the recording surface would help.

It's not completing the finalization so it won't play in a CD player yet.

It's mostly in the manual

http://www.retrevo.com/support/Harman-Kardon-CDR-20-CD-Players-manual/id/386dj191/t/2/

OPC: Stands for Optical Processing Calibration.

When you see this message in the Information

Display for the Record DeckK, it means

that the laser transport inside the unit is making

the calibrations and adjustments needed so that

the recording process is optimized for the specific
disc in use.

When an unfinalized CD-R or CD-RW disc is

placed in the Record Deck%, the letters

OPCwill flash once the Table of Contents has

been read. This indicates that the unit is optimizing

its circuits for maximum compatibility with

the specific recordable disc in use. the number

and total running time of any tracks that have

already been recorded will appear in the

Information DisplayK, and the appropriate

indicator SPwill light to tell you if a CD-R or
CD-RW disc is in use.

To Finalize a disc, place it in the Record

Drawer%. Once the disc's Table of Contents

information has been read and the OPC process

has been completed, press the Finalize button

E@and note that the Finalize Indicator

Uwill begin to flash. Within three seconds,

press the Select button9*and note that

the Finalize IndicatorUwill stop flashing.

The Finalization process will take up to two

minutes, depending on the length of material

recorded on the disc. During the Finalization

process the Record Deck will not accept any
operating commands.

Is the tape write-protected? If so, remove the protection.

This means exactly that these are copy Once only, meaning you can not make it copy say 10 copies, at the same time, it means you must do one a at a time. If you wanted say 10 copies, you must do the entire process over and over.

You can unlock by pressing and holding the Power switch. Sometimes it will then allow you to eject the disk after it restarts, but not always.

Try to run cleaning tape.

yes u hav eto use dvd +r disk ok try that 1st please thx nick

DVD's are burned from the center out, so if you're seeing a small band at the center, it sounds like the laser is overheating and quitting very early in the burn process.
No idea how to fix it, maybe blow it out with canned air?
Good luck, sorry I can't help more.....