c. Individual Characteristics. Each of us has individual voice characteristics that identify us as precisely as
our own name. Some of us speak slowly, others rapidly. Because of geographical differences in speech patterns,
some of us pronounce words differently.
(1) The average communication system is not capable of reproducing speech exactly as it originated.
Many systems are noisy. Therefore, the communicator must speak clearly and distinctly.
(2) Pronunciation of individual letters in the words has much to do with the ability of the listener to
understand the message. Vowels are clearly discerned most of the time, but consonants are not easily
understood because they are largely made up of high frequencies. If the communication system
cannot pass these high frequencies, there is distortion.
(3) The phonetic alphabet is often useful when voice communications are weak or noisy. The phonetic
alphabet is a system using words to denote letters. An entire word of the phonetic alphabet is given,
the first letter of which expresses the letter in question. (Example: "Delta" to express the letter D.)
Use of this alphabet allows positive identification of letters and reduction of errors and repetitions.
1-5. BASIC COMMUNICATION SYSTEM
a. Components. An electrical communication system must provide at least three basic components:
(1) An electromechanical device to convert information into electrical current variations. For example:
telegraph key, microphone, facsimile scanner, etc.
(2) An electrical connection, or transmission system, which will convey the electrical variations to the
distant point without altering their character greatly.
(3) An electromechanical device to convert the electrical current variations into mechanical or sound
wave motion.
b. Information Feedback. Feedback is the response returned to the source to acknowledge understanding or
provide requested information. A feedback system requires facilities for two-way transfer of information. Thus,
a communication system is not complete unless it provides two-way communications.
1-6. SYSTEMS FOR INFORMATION TRANSFER
The basic communication systems used to transfer information are telephone, facsimile, and telegraph. Voice
messages are transmitted over telephone circuits, visual images (photographs, maps, etc.) are transmitted over
facsimile circuits, and teletypewriter messages are transmitted over telegraph circuits.
a. Telephone Transmission. The telephone system is an example of a simple electrical communication
system. It consists primarily of a microphone, or transmitter, to convert sound waves to electrical signal, a
transmission line
4
Previous Page
