A signal tracer is a piece of

electronic test equipment Electronic test equipment is used to create signals and capture responses from electronic devices under test (DUTs). In this way, the proper operation of the DUT can be proven or faults in the device can be traced. Use of electronic test equipmen ...

used to

troubleshoot Troubleshooting is a form of problem solving, often applied to repair failed products or processes on a machine or a system. It is a logical, systematic search for the source of a problem in order to solve it, and make the product or process ope ...

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transm ...

and other

electronic Electronic may refer to: *Electronics, the science of how to control electric energy in semiconductor * ''Electronics'' (magazine), a defunct American trade journal *Electronic storage, the storage of data using an electronic device *Electronic co ...

circuitry. Usually a very simple device, it normally provides an

amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost th ...

, and a

loudspeaker A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or ...

, often battery-powered and packaged into a small, hand-held

test probe A test probe is a physical device used to connect electronic test equipment to a device under test (DUT). Test probes range from very simple, robust devices to complex probes that are sophisticated, expensive, and fragile. Specific types include t ...

. An optional diode

detector A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...

is usually also provided, allowing the detection of amplitude-modulated signals. The technician injects a test

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...

into the

device under test A device under test (DUT), also known as equipment under test (EUT) and unit under test (UUT), is a manufactured product undergoing testing, either at first manufacture or later during its life cycle as part of ongoing functional testing and calibra ...

. Then, by using the signal tracer, the tech can follow the signal through the various circuits of the radio receiver. So long as the signal can be heard, the circuitry up to that point is (at least minimally) functional. If the signal disappears, however, a fault can be assumed to be present in the stage of the circuit just passed. The diode detector is only sensitive to amplitude modulation but even circuits that are normally used for other modulation schemes (such as FM radios) can be tested by using an AM test signal for testing the

radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the uppe ...

circuits, then switching to an FM test signal (and switching out the diode detector) for testing the audio circuits of the radio. More sophisticated signal tracers may display

digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals **Digital camera, which captures and stores digital i ...

levels using, for example,

LEDs A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...

. For long pulse trains, a cyclic redundancy check may be calculated and displayed, giving the tech insight into the content of circuits that are switching rapidly.

References

Electronic test equipment {{tech-stub