Series I controls are pickup selector switch, neck pickup volume, neck pickup filter, neck Q switch, bridge pickup volume, bridge pickup filter, and bridge Q switch.
The selector switch chooses between neck pickup, both pickups, bridge pickup, and standby.
Basically, the filter control is a low pass filter; as you roll it back it lowers the point at which it passes low frequency signals and blocks high frequency signals. To quote Mica, the range is from 350Hz-6KHz. Wherever you set the filter, only frequencies below that cutoff point are passed. The Q switch is a 3 position switch and works in concert with the filter. It provides 0, 6db, and 9db of boost at the cut off frequency you've set with the filter. When the switch is off you get a flat response up to the filter setting. Again to quote Mica, the Q affects mainly the attack portion of the note.
The 5-pin connector provides power to the bass and sends a stereo signal (separate signals for the neck and bridge pickups) to the amp.
