Adtec digital EN-30 (version 1.02.02) Manual - Manual (Page 11)

A1 -A4 Off - Audio encoder configuration is set to off.
On - Audio encoder configuration is set to encode or passthru.
Blink - Audio pair is enabled but there is no payload on the input
System Indicators
Indicator Function
Alarm Off - No system alarms.
On - System alarm. (Typically NTP alarm)
BISS Off - No encryption set
On - Encryption active
Link Off - No network detected
On - Network communication active
Busy Off - No network activity
On - Network traffic present