BandLuxe K530 Series User Manual page 60

Appendix A: Vehicle Installation Guide
The Pi filter reduces transients by a specially designed RLC circuit, which
combines both capacitors and inductors utilizing transient-reducing
characteristics of both types of filters.
While any of the three types of filters will do the job, the Pi type is the
optimal choice, combining advantages of both capacitor and inductor
types of filters.
58