Hi I have a 1500 Kirk/ Spectralink dect system and i can't register 2 spectralink 7620 dect handsets, can anyone help me? thanks.

Holy smokes, it's been a long time since I've done that. Is there a particular point where you're getting stuck?

Hi I try to register but dont work, this 2 spectralink 7620 dect handsets are compatible?

It should be compatible.
Looking at the picture of the handset I did register some to a kirk 500 system.

https://support.spectralink.com/system/tdf/resource_files/user%20guide%2076series%2014184667%20ed%209%20%282%29.pdf?file=1&type=node&id=12504

Page 58 of the manual runs through howto register.

You'll need the ac code of the kirk 1500 system I beleive.
I Never did much with the 1500 system though.

Thanks i will try and comment with you