Also, I knew I had read something about that on wikipedia, here is the section from the article on Jazz basses.
A fourth push button control is available on American-made Jazz Basses produced between mid-2003 until 2008. Known as the "S-1 Switch", this feature allows the pickups to operate in standard, parallel wiring, or alternatively in series wiring when the switch is depressed. While in series, both pickups function as a single unit with one volume control, giving the Jazz Bass a sound more similar to the Precision Bass. The two pickups are built to be opposite from each other in both magnetic polarity and electrical phase, so that when heard together, hum is cancelled—the humbucking effect. The Highway One Jazz Bass is a moderately priced American-made bass introduced in 2003, featuring a Leo Quan BadAss II bridge with grooved saddles, Posiflex graphite neck support rods, 1970s styling and a Greasebucket tone circuit since 2006.
In 2008, the American Series models were replaced by a new American Standard line, which greatly differs from the first-generation American Standard Series basses introduced in 1994. The 2008 American Standard Jazz Bass retained the "American Series" rolled-edge neck with highly detailed nut and fret work, as well as the familiar rounded body shape with the vintage body radius, but deleted the S-1 switching system and incorporated a new high-mass vintage bridge, Hipshot lightweight vintage-style tuning machines, a richer and deeper neck tint, gloss maple or rosewood fingerboard and satin back for smooth playability. It also has a thinner finish undercoat that lets the body breathe and improves resonance. In March 2012 Fender updated the American Standard Jazz Bass (except the five-string version) with Custom Shop 1960s Jazz Bass pickups.
