ABSTRACT
Simulators and signal generators are tools serving to artificially create signals in various ways so that they can behave like true signals generated in processes, equipment, or instruments. The attenuator can reduce the signal amplitude to a known value through a previous calibration to match the source impedance or load. An extension of the frequency counter instruments with the electronic display is the electronic adjustment of the output frequency, called frequency synthesizer. Phase-locked loops (PLLs) are circuits for tracking the phase of a local signal generator with the phase of an external signal oscillator, regardless of the size or format of both. In the direct method of frequency synthesis, rather than generating a frequency for the phase difference between internal and external signals, the frequency is generated from a reference, while another frequency is derived from this one. Function generators, simulators, and audio generators are commonly used in laboratories for the analysis of low-frequency circuits.
