For lower SAPs only, controls whether this SAP appends the Transit Delay facility (with the value from x25SapTransitDelay) to incoming/outgoing calls that don't already carry one. Note: the source DESCRIPTION and option labels here are internally inconsistent -- the text talks about 'Calling Address Validation' (apparently copy-pasted from a neighboring object) rather than transit delay, and true/false are listed in the reverse order (true=1/subscribed, false=2/not-subscribed) compared to every other Sbscr* object in this MIB, so the DEFVAL of 'false' most likely maps to option value 2 as elsewhere; an admin should verify actual polled semantics against vendor documentation rather than rely on the literal description text for this one object.