How can an Auxiliary Circuit be identified?

• A. By the letter A as the first letter
• B. By the second letter being J
• C. By seeing X as the first letter of its designation (XJA - XJZ)
• D. By the designation ending with Z

Answer: (C)

Auxiliary circuits are identified by their designation prefix. On Navy sound-powered telephone diagrams, an Auxiliary Circuit starts with the letter X. Seeing a designation like XJA, XJB, XJC, up to XJZ means you’re looking at an Auxiliary Circuit. The first character is the key clue, so it doesn’t matter what the rest of the letters are—the defining mark is the leading X.

The other ideas don’t reliably identify Auxiliary Circuits: a different starting letter would indicate a different circuit class, the position of a letter (like the second letter) isn’t the standard identifier, and ending with a particular letter isn’t a universal rule for this purpose. So, the sure-fire way is to check for X as the first letter in the circuit’s designation.