ITFS was a band of twenty (20) microwave TV channels available to be licensed by the U.S. Federal Communications Commission (FCC) to local credit granting educational institutions.
In recognition of the variety and quantity of video materials required to support instruction at numerous grade levels and in a range of subjects, licensees were typically granted a group of four channels.
Subsequently, the FCC authorized ITFS licensees to lease a portion of their spectrum, designated as “Excess Capacity," for commercial use, meaning ITFS licensees were required to retain forty hours per week per channel for daytime instruction with the excess nighttime hours available for commercial use in exchange for technical and financial support for their instructional service.
So, primarily in large markets, subscription premium television such as HBO, Showtime, The Movie Channel and others could be transmitted over these same microwave stations beginning at 4 PM when school was out, and continuing throughout the evening, sometimes until the wee hours.
Only after ITFS had migrated to other formats did the daytime hours of the service become available to subscription television providers which filled the hours with programming such as the five-hour-long children's show Pinwheel airing weekday mornings on Nickelodeon or long blocks of international cartoons for which the rights thereto remained in the pennies per subscriber throughout the run of the technology.
These systems found, however, that the additional programming capability was not sufficient to overcome the line-of-sight handicap and the associated higher cost for customer installations.
These changes in rule and the rising demand for broadband communications led to several commercial tests of combined ITFS/MMDS digital systems designed for two-way data distribution.
Cellular phone pioneer Craig McCaw's Clearwire Wireless Internet Service Provider (WISP) leased EBS from the non-profit Broadcast license holder in many US cities.