Dahdi module clock sync

Hi
Hopefully an easy question, in the Dadhi module acessable from the conectivety menu, is sync source
0 for master (from the card) and 1 for normal (from the telco)
or is it the other way round?
I am going to install an Openvox D130e card here in the UK so any tips would be great.
Thanks in advance
Chazza