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Maya armies of the Contact period were highly disciplined, and warriors participated in regular training exercises and drills; every able-bodied adult male was available for military service. Maya states did not maintain standing armies; warriors were mustered by local officials who reported back to appointed warleaders.
Naval air traffic controller communicates with aircraft over a two-way radio headset A variety of portable handheld two-way radios for private use. A two-way radio is a radio transceiver (a radio that can both transmit and receive radio waves), which is used for bidirectional person-to-person voice communication with other users with similar radios, [1] in contrast to a broadcast receiver ...
The city of Tikal, later to be one of the most important of the Classic Period Maya cities, was already a significant city by around 350 BC, although it did not match El Mirador. [21] The Late Preclassic cultural florescence collapsed in the 1st century AD and many of the great Maya cities of the epoch were abandoned; the cause of this collapse ...
The Mayan calendar’s 819-day cycle has confounded scholars for decades, but new research shows how it matches up to planetary cycles over a 45-year span.
Satellite view of the Yucatán Peninsula. The Maya civilization occupied the Maya Region, a wide territory that included southeastern Mexico and northern Central America; this area included the entire Yucatán Peninsula, and all of the territory now incorporated into the modern countries of Guatemala and Belize, as well as the western portions of Honduras and El Salvador. [4]
A walkie-talkie, more formally known as a handheld transceiver, HT, or handheld radio, is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald Hings, radio engineer Alfred J. Gross, Henryk Magnuski and engineering teams at Motorola. First used for infantry, similar ...
The earliest communication with aircraft was by visual signalling, ground-to-air only. Air-to-ground communication was first made possible by the development of two-way aerial telegraphy in 1912, soon followed by two-way radio. By the Second World War, radio had become the chief medium of air-to-ground and air-to-air communication. Since then ...
The early history of radio is the history of technology that produces and uses radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio development began as "wireless telegraphy". Later radio history increasingly involves matters of broadcasting.