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If you have an invalid video reference feeding the Horus/Hapi physical Sync I/O port and have enabled connected it in the (with Easy Connect/ ANEMAN) then it will blink Yellow in Pyramix.
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TC ref: Connection must be enabled for Video reference.
If you don't have a valid video ref signal, disconnect TC ref from Easy Connect / ANEMAN.
Note: TC ref option must be enabled in order to lock the MassCore TimeCode to the Horus/Hapi Video In.