GE OPTIMA MR360 Service Training page 156

LED DS2, DS3, DS4 used to identify the Receiver Module number in binary format. LED DS1 is
used to indicate when the Mega Switch +3.3V incoming power is good and is not lit when
either the Mega Switch power is down or the cable into connector J1 is not connected. DS1
is used to prevent a false RRX1 indicator, where Port ID is equal to '000'. All of these LEDs are
powered by the Mega Switch +3.3V power.
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