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Wireless telegraphy or radiotelegraphy is the transmission of text messages by radio waves, analogous to electrical telegraphy using cables. [ 1 ] [ 2 ] Before about 1910, the term wireless telegraphy was also used for other experimental technologies for transmitting telegraph signals without wires.
The 77 bits are sufficient for free text messages of up to 13 text characters, reminiscent of SMS (TXT) messages or Tweets, while a clever data compression scheme reduces the number of digital bits required to pass structured messages containing conventional callsigns, reports and locators. Long or unusual callsigns are problematic for the ...
A teleprinter is a telegraph machine that can send messages from a typewriter-like keyboard and print incoming messages in readable text with no need for the operators to be trained in the telegraph code used on the line. It developed from various earlier printing telegraphs and resulted in improved transmission speeds. [37]
In larger metropolitan areas with congested frequency spectrum, paging services will often share the same frequency as land mobile stations, or operate on an adjacent channel. For example, a department store may operate handheld walkie-talkies on 462.7625 MHz while there are high power pager transmitters on 462.7500 MHz and/or 462.7750 MHz in ...
The discovery and application, early on, of frequency analysis to the reading of encrypted communications has, on occasion, altered the course of history. Thus the Zimmermann Telegram triggered the United States' entry into World War I; and Allies reading of Nazi Germany's ciphers shortened World War II, in some evaluations by as much as two years.
A digital secure voice usually includes two components, a digitizer to convert between speech and digital signals and an encryption system to provide confidentiality. It is difficult in practice to send the encrypted signal over the same voiceband communication circuits used to transmit unencrypted voice, e.g. analog telephone lines or mobile radios, due to bandwidth expansion.
Radioteletype tuning indicator Tuning indicator on cathode ray tube. Radioteletype (RTTY) is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations connected by radio rather than a wired link.
Source credibility is "a term commonly used to imply a communicator's positive characteristics that affect the receiver's acceptance of a message." [1] Academic studies of this topic began in the 20th century and were given a special emphasis during World War II, when the US government sought to use propaganda to influence public opinion in support of the war effort.