1971–1978: The First-Generation Interconnection System Starting in 1971, PBS began distributing programs via microwave relay circuits leased from
AT&T Long Lines. This was the first generation of PBS's interconnection system. Prior to this, PBS would distribute programs to stations via "bicycling tapes," meaning that tapes would be shipped between stations through the mail. The interconnection system consisted of nearly 20,000 miles of microwave paths spread across the country. Examples of these regional networks included the Southern Educational Communications Association (SECA), which is now known as the National Educational Telecommunications Association (NETA); the Central Educational Network (CEN); the
Eastern Educational Television Network (EEN), which is now known as
American Public Television (APT); and Midwestern Educational Television (MET). Another issue was that this system was single channel only, meaning that PBS could not feed multiple programs at the same time, giving stations less programming options. PBS began to inquire about the use of satellite for program distribution dating back to 1971. PBS quickly discovered the benefits satellite distribution would have on their operations. A satellite-based interconnection system would allow improved video and audio quality. This system consisted of four 15-KHz audio channels that would be "multiplexed" and transmitted via a "5.5-KHz subcarrier located above the video." Decoders for the DATE system cost up to $11,000 in the mid-1980s. PBS recommended that a station purchase at least two decoders, one of these acting as a backup unit. ($226,854,261.86 adjusted for inflation as of March 2026). The details of the contract with Western Union follow: Western Union split the country into various segments during the implementation phase. One primary advantage of Westar 4 was that it contained 24 transponders, compared to Westar 1's 12 transponders.
Direct/Dial Access Communication System (DACS) To communicate with stations, PBS launched a service called the
Dial (later Direct)
Access
Communications
System (DACS). DACS launched in 1981. DACS was transmitted in Line 13 of the
VBI of their satellite feeds. On July 21, 1995, a new communications system, known as PBS Express, launched. PBS Express launched alongside DACS, which would be discontinued in 1996. It is unknown what – if any – meaning the abbreviation "NOLA" has. A simple NOLA code is formatted as such: [NOLA 000000]. These codes are assigned to every public television program distributed by APT, NETA, and PBS. For example, the
Masterpiece series is assigned the NOLA code "MAST". Further, the complete NOLA code for episode one of the
Downton Abbey series (broadcast as season 41, episode 01 of the
Masterpiece franchise) would be: [MAST 004101]. Additional NOLA codes include "FRON" for
Frontline, "GPER" for
Great Performances, and "MLNH" for
PBS News Hour.
1987: Controversy Surrounding Potential Use of VideoCipher II During this time, PBS did not utilize any type of encryption on their feeds. However, beginning in mid-1987, PBS began to explore the possibility of encoding their feeds with
VideoCipher II. PBS, however, would encrypt the feeds anytime they aired what they referred to as "private communications," which include teleconferences and previews of programs that they haven't yet received broadcast rights for; all other programs remained unencrypted. On March 15, 1988, Bruce L. Christensen, the President of PBS at the time, appeared before a
Senate committee to discuss the proposed Public Telecommunications Act of 1988. This act included a provision stating that PBS must provide a "clear" feed of its programming to home-dish viewers who do not have a decoder. This act also created a committee to research and propose new plans regarding replacement of the satellite used for the interconnection system, known as the Public Television Interconnection Committee. Telstar 401 launched on December 16, 1993. PBS moved to Telstar 401, at orbital position 97°W, on February 5, 1994, ending primary program distribution to affiliates via C-band. AT&T tried to re-establish contact with the satellite, but all attempts failed. To restore service, PBS temporarily moved their feeds to Telstar 402R (later Telstar 4). To prevent noticeable interruption to their service, PBS carried out a Satellite Service Recovery Plan. During time on Telstar 402R, PBS began researching options to restore full service. Two proposals from Loral Space Systems and GE American were submitted to PBS for consideration. These proposals are listed below: On October 6, leased analog and digital services on TX #9 and TX #18, respectively, were added. On October 15, PBS's MCPC feeds, now encoded in DigiCipher II, would be added to TX #24 (same schedules as the DigiCipher I transponder with the addition of Schedule 8). The DigiCipher I MCPC transponder would be removed on November 2 and new DTV test feeds would be added to TX #7. TX #9 would also become the home of The Business Channel, in addition to other analog services. In mid-November, services on three transponders were moved to other transponders: services on TX 9 move to TX 19, the DTV feed moved from TX 7 to TX 21, and services on TX 3 move to TX 23. Once the move was completed in the beginning of 1998, PBS would own TX 18-24 on GE-3. In October 2012, PBS began encoding their feeds in the
DVB-S2 MPEG-4 codec, which they currently use. To help consider their options, they commissioned the help of Cognizant Technology Solutions to come up with a new cost-effective solution to improve the Public Television Interconnection System. A report discussing the proposed model for the sixth generation of the interconnection system was published in November 2015. The CPB tasked Vigor Systems, Inc. with developing and deploying the new interconnection system. Other codecs that are approved for use when delivering in HD are three versions of the
DNxHD codec: DNx145, DNx220, and DNx220x.
Transition away from satellite With initial tests of sIX throughout 2018 proving successful, PBS discontinued their NRT (non-real-time) file-based services on AMC-21, NR01 and NR02, created as part of the NGIS interconnection system, on January 2, 2019; with the closure of the NGIS NRT service, this marked the official launch of the sIX system. The goal was to move all linear-fed content to sIX in the near future. PBS has expressed that they will continue to lease transponder space for live and near-live programs, such as the
PBS NewsHour; PBS will also continue to lease transponder space in the event their sIX system suddenly fails or experiences an outage. As the transition to sIX has progressed, PBS began to shut down some of their NPS satellite distribution feeds. The first feed to shut down was PBS's SD01 service, shutting down on September 5, 2016; this occurred before the transition to sIX. Two years later, as previously mentioned, the NRT file-based service was shut down sometime near the end of 2018. On November 13, 2019, PBS discontinued their SD07 Ku-band service on AMC-21, which was uplinked from SCETV in
Columbia, South Carolina. All programming on SD07 could be found on HD04, albeit in HD. The transition to sIX accelerated in March 2021 when APT began to transition select programs off satellite and into the sIX system. In July 2021, programming from the NETA and APT migrated fully to sIX, ending distribution via satellite. However, two programs from APT –
Consuelo Mack WealthTrack and GZERO World with Ian Bremmer – continue to be fed via satellite on HD03 on Fridays. Program uplinks from KNME, with the exception of
Democracy Now! until the closure of the HD05 service on May 31, 2023, also migrated to sIX. PBS themselves had also migrated many regular, non-news linear feeds to sIX, including feeds of pledge programs, which were last fed in May 2021. The only content left on their three (at the time) primary NPS HD distribution feeds, HD03, HD04, and HD05, was news and public affairs programming. On July 21, 2021, a few weeks after this transition, PBS decommissioned two more satellite feeds, SD05 and SD06, at 2:56 p.m.
ET. On January 20, 2023, PBS's main transponder on AMC-21 (which included HD01-HD03, HD06, SD02, SD04, and SD08) began simulcasting on Galaxy 16, a satellite at orbital position 99°W. On May 3, 2023, a
ticker appeared on HD04 and HD05 alerting that both services would shut down on June 1, 2023, at 00:00
UTC (May 31, 2023, 8:00 p.m. ET); the ticker was later updated on May 25, 2023, with a new shutoff date of May 31, 2023, at 23:59:59 p.m. ET (11:59:59 p.m. ET). In the ticker, PBS said that program feeds on HD04 and HD05 would move to two new terrestrial-based services, HD64 and HD65. On May 31, 2023, at 11:58:52 p.m. ET, PBS completed the move to Galaxy 16. HD04 and HD05 were decommissioned at the same time. In 2024, PBS started testing new terrestrial feeds as part of their sIX interconnection system. These services are the same as the current satellite feeds on Galaxy 16 (HD01, HD02, HD03, HD06, Create, and World). A terrestrial feed of HD03 launched on the sIX platform in December 2024. FNX will be added at a later date. This is part of a new phase on the sIX rollout known as Phase F2, which is currently ongoing. It is not known whether PBS will decommission the satellite feeds once Phase F2 is complete. For now, stations record programs from both the satellite and terrestrial feeds, with one or the other acting as a backup. The sIX file-based system also acts as a backup.
sIX Rollout Phases The rollout of sIX is occurring in several phases: The report says that later stages will be "defined as business and technology needs evolve." • Phase F1 (2022 - May 31, 2023) involved transitioning feeds from the HD04 and HD05 satellite services to the new HD64 and HD65 terrestrial services. • Phase F2 (2023 - present) involves rolling out terrestrial services that mirror the services uplinked via satellite. ==Services==