PAL decoders for their SECAM sets. Eventually, the government in East Berlin stopped paying attention to so-called "Republikflucht via Fernsehen", or "defection via television". Later East German–produced TV sets, such as the RFT Chromat, even included a dual standard PAL/SECAM decoder as an option. Another explanation for the Eastern European adoption of SECAM, led by the Soviet Union, is that the Russians had extremely long distribution lines between broadcasting stations and transmitters. Long co-axial cables or microwave links can cause amplitude and phase variations, which do not affect SECAM signals. However, PAL and SECAM are just standards for the color sub-carrier, used in conjunction with ITU television broadcast systems for the base monochrome signals, identified with letters such as M, B/G, D/K, and L. These signals are much more important to compatibility than the color sub carriers are. They differ by AM or FM sound modulation, signal polarization, relative frequencies within the channel, bandwidth, etc. For example, a PAL D/K TV set will be able to receive a SECAM D/K signal (although in black and white), while it will not be able to decode the sound of a PAL B/G signal. So even before SECAM came to Eastern European countries, most viewers (other than those in East Germany and Yugoslavia) could not have received Western programs. This, along with language issues, meant that in most countries monochrome-only reception did not pose a significant problem for the authorities. Other countries, notably the United Kingdom and Italy, briefly experimented with SECAM before opting for PAL. SECAM was adopted by former French and Belgian colonies in Africa, as well as Greece, Cyprus, and Eastern Bloc countries (except for Romania) and some Middle Eastern countries. European efforts during the 1980-90s towards the creation of a unified an analog standard, resulting in the MAC standards, still used the sequential color transmission idea of SECAM, with only one of time-compressed U and V components being transmitted on a given line. The D2-MAC standard enjoyed some short real market deployment, particularly in northern European countries. To some extent, this idea is still present in 4:2:0 digital sampling format, which is used by most digital video medias available to the public. In this case, however, color resolution is halved in both horizontal and vertical directions thus yielding a more symmetrical behavior. With the fall of communism and following a period when multi-standard TV sets became a commodity in