What device is used to apply an audible electrical signal to a circuit for identification or fault location?

The tone generator is a device specifically designed to apply an audible electrical signal to a circuit, facilitating the identification of cables and the location of faults within a network. When connected to a circuit, the tone generator emits a distinct sound that can be easily traced using a compatible tone probe or receiver. This capability is especially useful for technicians and installers who need to identify cable runs or troubleshoot issues, as the sound helps differentiate between different lines and can guide users directly to the location of faults or breaks within a cable.

The other items listed do not serve this specific function. For instance, a shorting plug is used to forcibly short a circuit for testing purposes, and a transposed pair is a configuration used in cabling to minimize interference, not for signaling purposes. A bonding busbar serves to connect multiple grounding or bonding wires together, ensuring electrical safety but not for identifying faults or circuits. Thus, the tone generator is the ideal choice for the task of applying an audible signal for circuit identification.