CLASSIFICATION OF CIRCUITS
Sound-powered telephone circuits are divided into three
classifications based on their usage: primary, auxiliary, and
What are the three classifications of sound-powered
Primary circuits provide communication for primary control
and operating functions associated with ship control, weapons
control, engineering control, and damage control. Primary circuits
are designated by the letters JA through JZ. (Specific circuit
designations are labeled on the front of each jackbox.)
Auxiliary circuits duplicate certain principal primary circuits
as an alternate means of communication if damage occurs to the
primary circuit. The wiring of auxiliary circuits is separated as
much as practicable from the wiring of the corresponding primary
circuits. Auxiliary circuits have the same letter designation as
primary circuits, except they are preceded by the letter X.
Examples: XJA, X1JV, and X1JG.
What special precaution has been taken to prevent
simultaneous damage to both primary and auxiliary
How can you tell the difference between primary and
auxiliary circuit designations?
Supplementary circuits consist of several short, direct circuits,
such as those from the bridge to the quarterdeck or from the
quarterdeck to the wardroom. Supplementary circuits, designated
X1J through X61J, are normally string circuits. Circuits in