Interspace is a domain of reality that coexists out of phase with normal space as it borders parallel realities, and can be accessed through interphase effects.
History and specifics[]
Interspace transmission was used by the Furies to transmit a fear effect against Starfleet personnel at Brundage Point when they attempted to infiltrate the Alpha Quadrant in the year 2371. Some of the remedy that was used for previous interphase effects was successful in relieving the symptoms of the fear projector. (TNG - Invasion! novel: The Soldiers of Fear)
