Morse code was later made the standard by the International Telecommunication Union (ITU). Morse's original code specification, largely limited to use in the United States and Canada, became known as American Morse code or "railroad code". American Morse code is now seldom used except in historical re-enactments. In aviation, pilots use radio navigation aids. To ensure that the stations the pilots are using are serviceable, the stations transmit a set of identification letters (usually a two-to-five-letter version of the station name) in Morse code. Station identification letters are shown on air navigation charts. For example, the VOR-DME based at Vilo Acuña Airport
Braille pattern dots-124 Braille pattern dots-124 The Braille pattern dots-124 ( ) is a 6-dot braille cell with the two top dots and middle left dot raised, or an 8-dot braille cell with both top dots and the upper-middle left dot raised. It is represented by the Unicode code point U+280b, and in Braille ASCII with F. In unified international braille, the braille pattern dots-124 is used to represent unvoiced labial fricatives, such as /f/ and /ɸ/, and is otherwise assigned as needed. It is also used for the number 6. Related to Braille pattern dots-124 are Braille patterns 1247, 1248, and 12478,