Alcatel Unleashed

Hi, we have alcatel 4020 handsets at my work place. Some of them are old and showing some wear. I've bought some replacements on ebay but unsure how to programme them. Specifically on our current phones one of the buttons is programmed to activate DTMF tones during a call. How do I set this up on the replacements?

4020 - digital set, works with OXE or OXO PABX. If you want to change set - just connect new one. You need nothing to program. All management stored in PABX (nothing in set). After changing - new set works 100% like previous one.

Thanks vad, I will try just swapping them out.