LESSON 3
CARRIER COMMUNICATION
SCOPE........................................................................... Combining of communication channels on a common
line; frequency translation; telephone and telegraph
multiplexing principles.
CREDIT HOURS ........................................................... 1
TEXT ASSIGNMENT ................................................... Attached Memorandum, para 3-1 thru 3-9
MATERIALS REQUIRED............................................. None
SUGGESTIONS............................................................. None
LESSON OBJECTIVES
When you have completed this lesson, you should:
1. Know that several channels of communication can be combined on a pair of wires by the process of
multiplexing.
2. Know that an integrated communication system includes multiplexing carrier terminals together with radio
relay sets.
3. Know that a radio system and a carrier system operate on similar principles but different frequencies.
4. Be able to analyze a block diagram of an integrated communication system.
5. Be able to distinguish the difference in operating principles between frequency-division and time-division
multiplex.
ATTACHED MEMORANDUM
3-1. CARRIER PRINCIPLES
Nearly all types of electrical communication systems use the carrier communication principle in one form or
another. Depending on the traffic requirements, the terminals may be single-channel or multichannel. In most
cases the carrier frequency is supplied by an oscillator. Whatever the frequency chosen for the carrier, it should
be at least 10 times the highest frequency used for modulating it. The interaction of the carrier and modulating
frequency produces an amplitude-modulated frequency-modulated or phase-modulated signal, depending on the
system design. In the receiving process the sequence is reversed, the signal intelligence being extracted by
demodulation. System characteristics of any carrier system are to a large extent determined by the carrier
frequency.
22
Previous Page
