The TO1000 series oscilloscopes have a peak input voltage of 100V. If the probe attenuation is set to 1:1 (1X), then the user must ensure that the maximum voltage to be probed is 100V. A higher attenuation setting of the probe (assuming the probe is rated for the voltage to be probed) will allow the user to probe voltages that are higher than the value the scope input that is allowed. This is made possible due to the probe attenuation. If the user were to want to test a circuit with voltages in the 400V peak value, the user could use a probe with a 10X setting, and this would present a 40V peak value to the oscilloscope.
If the probe has adjustable attenuation values, the user has to ensure not to switch from the higher to lower attenuation value while probing a circuit with voltages that exceed the scope input rating.