What is the proper tool for measuring whether a signal is being received from one portion of a circuit to another?

The correct tool for measuring whether a signal is being received from one portion of a circuit to another is a butt set. A butt set is specifically designed for testing and troubleshooting telephone lines by connecting directly to the line and allowing the technician to listen for signal presence and perform various testing tasks. This functionality is essential in verifying that signals can travel through the circuit as expected.

While other tools like a multimeter and an oscilloscope can measure voltage or detect signals, they do not provide the same specificity for checking the integrity of telecommunication circuits in a hands-on manner. A multimeter can measure electrical values such as voltage, current, or resistance, but it does not typically allow for active signal monitoring. Similarly, an oscilloscope can visualize signals in terms of waveforms, but it is not directly used for indicating signal presence or for real-time telephone line testing.

A wattmeter measures electrical power in circuits and is not applicable for confirming signal transmission in the way that a butt set does. Thus, the butt set stands out as the proper tool for this specific purpose in circuit testing and verification.