.рф

The domain name рф (romanized as rf ) is the Cyrillic country code top-level domain for the Russian Federation, in the Domain Name System of the Internet. In the Domain Name System it has the ASCII DNS name xn--p1ai. The domain accepts only Cyrillic subdomain applications, and is the first Cyrillic implementation of the Internationalizing Domain Names in Applications (IDNA) system. The domain became operational on 13 May 2010. As of 2014 it is the most used internationalized country code top-level domain with around 900,000 domain names.

Character set

рф (Russian: Российская Федерация) is transliterated as Rossiyskaya Federatsiya, the Russian Federation. The domain has an ASCII representation of xn--p1ai derived as Punycode for use in the Domain Name System.

The domain is intended for Internet resources with names in the Russian language using Cyrillic.

A principle in the approval process of ICANN Generic Names Supporting Organization (GNSO) states that Cyrillic two-character top-level domains should not exclusively use characters that could be confused with Latin characters of identical or similar shapes—not just those containing the seven letters а, е, о, р, с, у, and х, but also proposed ccTLDs such as .бг (Bulgaria) due to its visual similarity to .br. As such, GNSO sought to avoid the direct transcription of "ru" into Cyrillic, "ру", and common abbreviations for Russia (Russian: Россия), such as "ро", in order to avoid confusion with the Latin ccTLDs .py (Paraguay) and .po (currently unassigned). In English sources .рф can be romanized as .rf, but the latter is not a valid domain for Russia. More recently, four other countries have won approval of three-letter Cyrillic ccTLDs such as .укр, .срб, .мон and .қаз. As of today .рф remains the only Cyrillic ccTLD with two letters.

Radio frequency

Radio frequency (RF) is any of the electromagnetic wave frequencies that lie in the range extending from around 7003300000000000000♠3 kHz to 7011300000000000000♠300 GHz, which include those frequencies used for communications or radar signals. RF usually refers to electrical rather than mechanical oscillations. However, mechanical RF systems do exist (see mechanical filter and RF MEMS).

Although radio frequency is a rate of oscillation, the term "radio frequency" or its abbreviation "RF" are used as a synonym for radio – i.e., to describe the use of wireless communication, as opposed to communication via electric wires. Examples include:

Special properties of RF current

Electric currents that oscillate at radio frequencies have special properties not shared by direct current or alternating current of lower frequencies.

List of minor planets: 85001–86000