 PBS and CPB rules permit underwriting commercial use for broadcast stations with certain speech limits that are only required of broadcast stations because of the nature of the non-profit license.Channels that run non-commercial formats on cable television or direct broadcast satellite television tend not to use underwriting spots, as they can use subscriber fees to fund operations (such as C-SPAN).Classic Arts Showcase is an exception, as the service is funded through a foundation established by its founder, Lloyd Rigler, and thus credits that foundation for its funding on-air.