Design of equipment in which ce is suppressed
Approved installation criteria that limits interaction between classified and unclassified signal
lines, power lines, grounds, equipment, and systems
Low level keying and signaling
Shielded enclosures for equipment installations
Proper shipboard grounding of equipment, including ground straps
Transmission security includes all measures designed to protect transmission from interception,
traffic analysis, and imitative deception. Every means of transmission is subject to interception. In radio
transmission, it should be assumed that all transmissions are intercepted.
Speed Versus Security
Three fundamental requirements of a military communications system are reliability, security, and
speed. Reliability is always first. Security and speed are next in importance and, depending on the stage of
an operation, are interchangeable. During the planning phase, security is more important than speed.
During the execution phase, speed sometimes passes security in importance.
Radio Transmission Security
When a message is transmitted by radio, the originator may know some of those who are receiving it,
but will never know all of those who are receiving the message. You must assume that an enemy receives
every transmission. Property prepared messages using modern cryptographic systems may prevent an
enemy from understanding a message. However, they can still learn a lot. For example, as time for a
planned operation approaches, the number of messages transmitted increases. An enemy then knows that
something will occur soon, and their forces are alerted. Strict radio silence is the main defense against
The amount of radio traffic is not the only indicator used by an enemy. Statistical studies of message
headings, receipts, acknowledgments, relays, routing instructions, and services are also used by an enemy.
Communications experts can often learn much about an opponent from these studies. Direction finders
are another aid the enemy can use to determine where messages originate.
Radiotelephone networks are operated so frequently that many operators tend to be careless. There
are too many instances of interception of vhf and uhf transmissions at distances of many thousands of
miles. You may have occasion to work on or around this type of equipment. If you are ever required to
bring any transmitter on the air for any purpose, you must be familiar with and use all the correct
Q31. The transmission of still images over an electrical communications system is known as what?
Q32. The term TEMPEST refers to what?
Q33. What are the three fundamental requirements of a military communications system?
Q34. Which of the above requirements is most important?