In Witt v. Commonwealth, 15 Va. App. 215, 220, 422 S.E.2d 465, 469 (1992), the Court held that the prosecution had properly authenticated audio tapes of conversations between the defendant and a police informant. A prosecution witness testified that he transferred some of the conversations from reel to reel tapes to cassette tapes, that a typist transcribed the contents of all the recordings and that he reviewed the typist's work to ensure its accuracy. Id. Such testimony "sufficiently showed" that the "tapes had not been altered or substituted." The informant, who participated in the taped conversations, testified that the tape recordings were accurate. Id. The Court required no technical testimony about the range or power of the recording devices.