were able to secure the national retransmission rights (including some held over from before the SyndEx law was enacted), and supplementary programs acquired specifically for the national cable feed to absolve any holes caused by exclusivity claims—as well as separate national advertising, and in the case of WWOR, local advertising sold by individual cable systems. This would be achieved by "splitting" the signal, often requiring the use of a separate transponder to switch between the local feed and the alternate programming feed, so that certain programs viewed in the station's home market could be easily replaced with separate content that would only be shown over the national cable feed. While United Video made efforts to clear as much of the programming seen on the WGN Chicago feed as it possibly could, EMI increasingly filled the national WWOR EMI Service feed with library content distributed by Universal Television, MGM Television and Quinn Martin—consisting of classic television series from the 1950s to the 1970s—as well as select programs from the Christian Science Monitor television service, alongside shows on WWOR's local program schedule that it was able to acquire retransmission rights at the national level (including local newscasts, sports and other WWOR-produced programming as well as special events, the station's overnight simulcast of the Shop at Home Network and a limited number of syndicated shows that did not have exclusivity claims in any market). Confusingly for WWOR's national cable viewers, on-air promotions for programs not contracted to air nationally over the EMI Service were shown unaltered during simulcasts of programs aired on the New York signal. (This was not an issue with the WGN national feed, as United Video chose to substitute program promotions for shows airing on the Chicago signal that were not cleared on the national feed with those for the replacement shows exclusively seen on the latter, albeit still using station logos and promotional graphics used by the Chicago broadcast feed). To blunt potential subscriber complaints over widespread programming blackouts, many cable systems removed both regional and quasi-national superstations (like WSBK, WPIX and KTVT) as well as other distant signals that their satellite carriers were unable or unwilling to take immediate steps to ensure their programming was "Syndex-proofed" to avoid blackouts. WGN and WTBS saw little negative impact to their distribution following the Syndex implementation, with WGN actually heavily benefiting from provider removals of other superstations (including then sister station