PAL LaserDiscs have a slightly longer playing time than NTSC discs, but have fewer audio options. PAL discs only have two audio tracks, consisting of either two analog-only tracks on older PAL LDs, or two digital-only tracks on newer discs. In comparison, later NTSC LDs are capable of carrying four tracks (two analog and two digital). On certain releases, one of the analog tracks is used to carry a modulated AC-3 signal for 5.1 channel audio (for decoding and playback by newer LD players with an "AC-3 RF" output). However, older NTSC LDs made before 1984 (such as the original DiscoVision discs) only have two analog audio tracks.