This read-only object is the index (1-4) for the demodulator to which a row of circuit ID configuration applies. This lets each of up to four demodulators carry its own distinct circuit identifier, which matters on a unit terminating multiple independent satellite circuits where each needs to be individually identifiable in inventory and trouble-ticketing systems rather than sharing one label for the whole chassis. A technician configuring the circuit ID for the link on one specific demodulator needs to address the table row keyed by that demodulator's index rather than assuming a single circuit ID applies to the whole unit.