Which code denotes Call on signal light control detector?

• A. CG
• B. CO
• C. CH
• D. COS

Answer: (A)

Two-letter codes in signal maintenance act as shorthand labels for specific detector or control devices, letting technicians quickly identify parts on diagrams, test sheets, and in the field. For a detector that monitors the call-on signal used to control signal lights, the standard label is CG. That mapping matches the described function precisely, which is why it’s the correct choice. The other codes are used for different components or subsystems and don’t correspond to the call-on signal light control detector, so they wouldn’t be used for this function. In practice, always refer to your department’s code legend, but CG is the label you’ll see for the call-on signal light control detector.