A guitar pickup that requires powered electronics (usually a preamp powered by one or two 9-volt batteries) on board the instrument in order to function. Active pickup/preamp systems may provide buffering, EQ, feedback control, filtering, and level boosting, as well as lower noise and hum than passive designs. Most active pickups do not require a string ground, protecting the player from electrocution/shock dangers.
Active pickups are popular on bass guitars and acoustic guitars (which often combine piezo pickups with preamps), as well as on certain types of solidbody electric guitars.