This read-write object masks or unmasks the Rx-AIS alarm: unmasked(0) or masked(1). This suppresses alerting when AIS is detected on incoming, received, data, meaning the far end is itself reporting an upstream fault into this link, and masking it only makes sense if that condition is already tracked elsewhere, since otherwise a genuine problem originating at the far end's own terrestrial interface would go silently unreported here. If the far-end site's own terrestrial equipment fault reporting already captures and escalates AIS conditions independently, a local admin might mask this redundant Rx-AIS alarm here to reduce noise in this modem's own alarm log.