In People v. Bialostok (80 NY2d 738 [1993]), the Court of Appeals first confronted the issue of the suppression of pen register evidence in the context of a seizure without any prior judicial approval. While the Bialostok decision postdates the enactment of CPL article 705, the surveillance in question had been done prior to the enactment and thus without warrant. The electronic devices employed in Bialostok were similar to those used in the instant case in that they were convertible from digital to aural interception. On this set of facts, upon which defendants rely, it was determined that a convertible pen register was the equivalent of an eavesdropping device and (id. at 742): "unless a warrant is obtained for instruments such as these, which were capable of monitoring conversations, the evidence must be suppressed." The Court suppressed the pen register evidence both as direct evidence and as derivative evidence to support a probable cause determination on a later issued warrant. The Bialostok decision, read by the various Appellate Divisions as a per se rule banning the use of convertible devices, led to a series of cases which suppressed both direct and derivative evidence gathered by convertible surveillance devices.