ABB ProtectIT REL 551 2.5 Installation And Commissioning Manual page 72

Configuring the short range fibre optical
modem
Table 5: Indications
LED Color Explanation
RTS Yellow Request to send
CTS Yellow Clear to send
DSR Yellow Data communication correct
DCD Yellow Detection of carrier signal
TXD Yellow Transmitted data
RXD Yellow Received data
RA Red Remotely detected problem with link
MA Red Memory function for problem with link
LO Green Link operation correctly
LA Red Locally detected problem with link
Sync Green Used when synchronization is selected
Chapter 8
Configuring the 56/64 kbit data
communication modules
63