During the Second World War, the Marine Corps Command of the United States was confronted by a difficult problem of providing secrecy of communicated messages.

We are focused on a telephone set not as a system for transmitting and receiving voice information but on a telephone set as a final element of the entire process, which is in direct contact with a user.

Russian inventors found a new simple and inexpensive method for information transmission for great distances.

Among the fortifications of an ancient fortress in the Korean city of Suvon, there is a high massive construction with five cylindrical towers.