The 4040 is a Function Generator from BK Precision. A function generator is a type of signal generator people use to generate many kinds of electrical waveforms over a range of frequencies. A function generator is a type of electronic test equipment that produces sine, triangular, square, and sawtooth shape waveforms. The user can make these waveforms single-shot, using a trigger source, or repetitive, based on use. This kind of signal generator uses integrated circuits to create waveforms. Function generators cover both RF and Microwave frequencies.