[?]: SIEMENS 103 protocol for distance relays 7SA5221

[mytom123]

Hi
Any body give me advise about this problem:
I have some distance relays : 7SA5221-6CB32-4HR4 that support IEC103 protocol with port B (fibre optical 1 channel).
I have tested each relays and it worked fine.
I try to connect in serial all relays but after that it do not work.
So the siemens relay only support connect in serial by FO if port B has 2 channel ?
With only 1 channel, i have to connect directly to master? or..

Brgds.