This object specifies the forward signal indicating the call originates from a subscriber's line accorded priority call treatment, restricted specifically to national trunks per the R2 spec. Priority marking here protects the call from being the first dropped during congestion, so this signal is a meaningful safeguard for critical subscriber lines, such as hospitals or government offices, but only within national trunk contexts; it explicitly does not apply to international routing. A hospital's outgoing line configured with priority status would generate this forward signal on national calls, helping it survive trunk-group congestion that would block an ordinary subscriber's call.