Although PBS (a.k.a. the
Public Broadcasting Service) is the largest and best known example of
public television, it isn't the only one in America.
American Public Television is another semi-network of semi-affiliated public television stations in the U.S. The APT National Carriage Service tracks a program's scheduled air dates among nearly 350 public television stations nationwide to help producers with underwriting, station relations and marketing efforts.
Their standards are more lax in terms of format and funding; as a result, many smaller public television stations in
rural areas belong to APT instead of PBS. APT as an organization actually predates PBS by almost a decade.
One of their primary services is the APT National Carriage Service, which tracks a program's scheduled air date among nearly 350 public television stations nationwide to help producers with underwriting, station relations and marketing efforts.
APT has been criticized on occasion for their relaxed funding standards, which has on more than one occasion lead to "embedded" or "hidden" sponsorship of programs which the funder has a vested interest. Imagine, for example, a documentary on American obesity sponsored by Pfizer that also might include a subtle plug for a newly released Pfizer diet pill; something that wouldn't pass muster on PBS itself.
Over the last decade, private cable networks have seriously eroded public television's traditional audience. With the Learning Channel producing nature documentaries, the History Channel producing historical biographes and A&E producing cultural programming, public television is struggling to make ends meet in a highly competitive environment.
As a result, it's likely that embedded and hidden corporate sponsorship of programming will likely increase as standards for funding of programming continues to be relaxed.