The TA044 is a 70MHz high-voltage Active Differential Probe with 100:1 and 1000:1 attenuation ratio. They let you use a conventional earthed oscilloscope to measure signals that are not referenced to ground, including mains voltages. They can also be used to measure and observe the waveforms of three-phase supplies or the gate and control signals of semiconductor circuits. They are ideal for investigating motor speed controls, uninterruptible power supplies, switch mode power supplies and process controllers.