This is the index (1 to 4) for the Rx table, identifying which of the unit's satellite receive paths a given row of RF configuration applies to. This index is what allows a single MIB table to describe up to four independent demodulator configurations, like frequency, symbol rate, and FEC, on a multi-demodulator CDD-564, letting a management station address each demodulator's settings individually. An admin configuring demodulator 2 specifically to a different Rx frequency than demodulator 1 would set this index to 2 before applying the frequency change.