Laserdiscs have two separate audio tracks, one digital and one analogue. Normally, the digital track carries a 16-bit 44.1kHz PCM digital stereo signal and the other carries analogue stereo (usually with CX noise reduction).
For laserdiscs that include an AC3 5.1 track, that signal is contained in RF-modulated form in one of the analog channels. The other analog channel usually has either a mono sound mix or an audio commentary, and the digital track contains the 2-channel stereo or matrixed Dolby Surround mix.
Some discs even have a DTS bitstream on the digital track instead of 2-channel PCM. These discs are still sought-after and generally sell for a high price.
Now, there are various different connections you might find on the back of a laserdisc player. The most common are a pair of RCA jacks that output a standard analogue audio signal - colour coded red (right channel) and white (left channel). These could output either the analogue track or the digital track, selectable by the user (the V8000 actually has two sets of jacks, so it could output both tracks at the same time).
A single RCA labeled "AC3 RF" or similar outputs the RF-modulated AC3 off the analogue track. This needs to be demodulated to convert to an AC3 bitstream that can be decoded by a Dolby Digital decoder.
A digital optical TOSLINK or digital coaxial RCA jack outputs either 2-channel PCM or DTS in digital form (DTS does not need to be demodulated).