The device used to activate the wormholes to enable sliding is an old modified Motorola cellphone, the MicroTAC. The new device acquired to slide in season three appears to be a common television remote control. The device used for sliding in "Exodus" parts I and II is a modified Sega Genesis controller.
Even though the production of the show went on continuously between seasons three and four, it had a year hiatus from airing when it was dropped by FOX, and picked up by Syfy, making the airing years (1995-1997, 1998-2000). The visual effects in the fourth season take a very noticeable dive in quality, as the series had just been canceled by FOX, before being resurrected by the Syfy Channel, which left the show with an overall lower production budget.
Jerry O'Connell (Quinn) wrote an episode treatment titled "Narcotica", which took place on an Earth where drugs had been legalized. The story was rejected by the network for being "too dark", but later found life as a "Sliders" comic book.