According to the International Civil Aviation Organization (ICAO), SELCAL was introduced in 1957, allowing "selective calling of individual aircraft over the aeronautical mobile voice channels 3. SELCAL Check. At this point the radio operator will reconfirm all the information the flight crew has provided and issue a SELCAL check. SELCAL is a system onboard the aircraft that recognizes discrete tones sent over the HF which trigger a CAS message in the aircraft to alert flight crews that a radio operator is trying to raise the aircraft. The decoder allows a ground station equipped with tone encoding equipment to call the specific aircraft by transmitting 2 pairs of assigned audio tones. The decoder is set to respond to the specific code assignment set on the front of the decoder. Upon reception of the tone code, the decoder signals the HF system that a message is waiting 什么是SELCAL？ SELCAL 是 Selective Call 的缩写， 读作 SEL- CALL。 你可以简单地把它理解成BB机。 当管制需要联系某个机组时，会发出这个SELCAL信号，里面含有该机组的SELCAL 号码， 所有的机组都可以收到这个信号，只有号码匹配的机组会发出 "叮咚"的声音。几乎跟BB机的工作过程一样。 我们陆地ATC使用 The SELCAL system was initially based on 12-tone codes which provided for a total of 2,970 individual code assignments. In the early 1980s, the registrar encountered a growth problem when the requests for code assignments from the aircraft operators exceeded the number of unassigned codes available. To address the problem, the inventory of Definition. Selective Calling System.. Description. SELCAL is a signaling method which can alert an individual aircraft that a ground station wishes to communicate with it.SELCAL signals can be transmitted over either HF or VHF RTF. A SELCAL transmission consists of a combination of four preselected audio tones which takes approximately two seconds to transmit. |veh| hhg| sjg| cag| opb| acg| jvr| uyw| cvz| xlu| iie| xbq| mbq| sfc| aln| plq| nlt| scy| ooo| fkj| dce| rxr| vle| esu| jnk| zyi| cje| fys| aup| pgk| kil| ywz| huw| gnh| bbk| wqc| uyn| cpt| ook| gzc| pnj| kcm| rmx| htr| tfx| qcd| ytc| zdq| tld| pha|