How do I know which TensRelief setting is right for me?

Conventional TENS is a common TENS program with high-frequency stimulation. It is based on the Gate Control Theory that states that this type of stimulation will cause the transmission of pain signals in the nervous system to be blocked. It is comparable to 'rubbing the pain away'. Most people use Conventional TENS for 30 minutes per session, but you can use it as often and as long as you feel comfortable with. The effect is usually most perceptible during stimulation. The effect generally wears off rather quickly when stimulation has ended. You should adjust the intensity of the program so that you clearly feel the stimulation. However, stimulations should not give an unpleasant or painful sensation.

Burst TENS offers a high-frequency stimulation that comes in trains of pulses. You can use burst TENS around 30 minutes multiple times a day, for example, 3 times. It is advised that you adjust the intensity of the burst program so that you strongly feel the stimulation. Generally, burst programs give a sharper sensation which can feel somewhat unpleasant. It is also advised to adjust the intensity to a level where it gives you visible muscle contractions in the stimulation area. This is not harmful, but if you find these contractions too uncomfortable, you can decrease the intensity, choose a different program or move the electrodes to a different place.
Important note: burst TENS should always be applied while resting, as it can result in muscle contraction in the stimulation area.

Frequency-modulated TENS is a program where the frequency of the pulse varies from high to low, which can be more comfortable or effective than the other programs in some cases. You can use frequency-modulated TENS for around 30 minutes multiple times a day, for example, 3 times. It is advised that you adjust the intensity of the program so that you clearly feel the stimulation. Stimulation should not give an unpleasant or painful sensation.

See also the table from the user manual.