What device sends pulses into a cable to display reflections caused by changes in electric characteristics?

The device that sends pulses into a cable to display reflections caused by changes in electrical characteristics is a radar. In the context of cable testing, a radar system can utilize Time Domain Reflectometry (TDR) to send electrical pulses through the cable. When these pulses encounter changes in impedance, such as breaks or faults in the cable, a portion of the pulse is reflected back to the source. The radar then measures the time it takes for these reflections to return, allowing technicians to locate issues along the cable's length accurately.

This method is vital in various applications, such as telecommunications, where it helps identify and troubleshoot problems in the cable network effectively. The device's ability to analyze the time intervals and shifts in the reflected pulses provides crucial information about the condition and quality of the cable, ensuring maintenance and repair tasks can be performed efficiently.

In contrast, other devices like a multimeter primarily measure voltage, current, and resistance; an oscilloscope displays waveforms of signals but does not provide the same level of cable fault analysis; and a transformator (transformer) is designed to transfer electrical energy in a circuit, rather than to analyze reflections in a cable. Therefore, radar is the appropriate device for this specific application.