This read-write object indicates whether to accept, transfer, and deliver an unknown Information Element from the calling party when that IE's own action-instruction flag permits pass-through, though if the flag instead demands the IE be acted on, that instruction is followed regardless of this setting. It specifically controls forward compatibility with newer or vendor-specific IEs this switch doesn't itself recognize, letting them reach an end device that might understand them even if this switch doesn't. A newer signaling extension IE the switch's software doesn't recognize, but whose flag permits pass-through, would still reach the called party intact if this is enabled, preserving forward compatibility with newer far-end equipment.