a limited subset of features found in the majority of all ALE radios and controllers. Each amateur radio ALE station uses the operator's call sign as the address, also known as the ALE Address, in the ALE radio controller. The lowest common denominator technique enables any manufacturer's ALE radios or software to be used for HF interoperability communications and networking. Known as Ham-Friendly ALE, the amateur radio ALE standard is used to establish radio communications, through a combination of active ALE on internationally recognized automatic data frequencies, and passive ALE scanning on voice channels. In this technique, active ALE frequencies include pseudorandom periodic polite station identification, while passive ALE frequencies are silently scanned for selective calling. ALE systems include Listen Before Transmit as a standard function, and in most cases this feature provides better busy channel detection of voice and data signals than the human ear. Ham-Friendly ALE technique is also known as 2.5G ALE, because it maintains 2G ALE compatibility while employing some of the adaptive channel management features of 3G ALE, but without the accurate GPS time synchronization of 3G ALE. Disaster relief HF network Hot standby ALE nets are in constant operation 24/7/365 for International Emergency and Disaster Relief communications. The Ham Radio Global ALE High Frequency Network , which began service in June 2007, is the world's largest intentionally open ALE network. It is a free open network staffed by volunteers, and used by amateur radio operators supporting disaster relief organizations. International coordination International amateur radio ALE High Frequency channels are frequency coordinated with all Regions of the International Amateur Radio Union (IARU entity of ITU), for international, regional, national, and local use in the Amateur Radio Service. All Amateur Radio ALE channels use "USB" Upper Sideband standard. Different rules, regulations, and bandplans of the region and local country of operation apply to use of various channels. Some channels may not be available in every country. Primary or global channels are in common with most countries and regions. International channels This listing is current as of February 2020. See HFLINK for more information about Amateur Radio Service ALE Automatic Link Establishment. Frequency table notes: Automatic Link Establishment ALE channel frequencies in the Amateur Radio Service are internationally coordinated with selective calling Selcall channels for interoperability purposes. Net is the ALE net address or Selcall net name. Standard configurations International nets See also Multiple frequency-shift keying Selective