TENS Modes Explained: Burst, Normal, Modulation, SD1 & SD2
Burst, Normal, Modulation, SD1, and SD2.
These are not merely different intensity levels. Each mode changes how the electrical pulses are delivered over time, which is why switching modes can make stimulation feel noticeably different even when the electrodes remain in the same locations.
The Balego TENS Digital Edition is a dual-channel, over-the-counter TENS device cleared by the FDA for temporary relief of pain associated with sore and aching muscles in the low back and upper or lower extremities caused by strain from exercise or normal household and work activities.
This guide focuses specifically on what the five TENS modes mean, how they differ electrically, and what you should understand before changing from one mode to another.
TENS modes at a glance
| TENS mode | What changes | Pattern | Main distinction |
|---|---|---|---|
| Normal | No automatic modulation | Continuous pulses | Most consistent pattern |
| Burst | Pulses are grouped into bursts | Rhythmic pulse groups | Distinct on/off-like pulsing sensation |
| Modulation | Pulse rate and pulse width automatically vary | Repeating 1-second cycle | Pattern changes continuously |
| SD1 | Intensity and pulse width vary in opposite directions | 10-second cycle | 40% strength-duration variation |
| SD2 | Intensity and pulse width vary in opposite directions | 10-second cycle | Larger 70% strength-duration variation |
1. Normal Mode: steady TENS stimulation
Normal is the most straightforward Balego TENS mode.
Instead of automatically varying the stimulation pattern, Normal delivers continuous pulses according to the selected settings. The pulse rate and pulse width remain at their chosen values until the settings or mode are changed.
| Normal Mode characteristic | TENS behavior |
|---|---|
| Pulse delivery | Continuous |
| Automatic variation | None |
| Pulse rate | Remains at selected setting |
| Pulse width | Remains at selected setting |
| Typical perceived pattern | Steady, repetitive stimulation |
This predictability makes Normal a useful reference point for understanding the other four modes: Burst changes when groups of pulses arrive, while Modulation, SD1, and SD2 deliberately vary electrical parameters over time.
The Balego TENS Digital Edition uses the term "constant" or "normal" to describe this steady pattern.
Normal does not mean “maximum” or "strongest."
Normal describes the pattern, not the intensity.
The two amplitude controls on the Balego TENS determine how strong stimulation feels on each active channel. Selecting Normal does not automatically produce more or less output than another mode.
2. Burst Mode: pulses delivered in groups
Burst Mode reorganizes the stimulation into rhythmic groups of pulses.
Instead of one continuously repeating sequence like normal, the Balego platform delivers multiple individual pulses together as a burst, followed by an interval before the next burst.
The EV-804 technical specification associated with the BAL820 platform documents:
| Burst specification | Documented behavior |
|---|---|
| Frequency inside the burst | 100 Hz |
| Adjustable burst rate | 0.5–5 Hz |
| Pulse width | Adjustable within the device's permitted range |
| Pattern | Groups of individual pulses |
The waveform illustration makes the difference particularly clear: "Normal" presents regularly spaced pulses, whereas "Burst" collects pulses into separated clusters.
What does Burst Mode feel like?
Because the pulses arrive in groups, users may perceive Burst as more rhythmic or pulsating than the steady sensation of Normal.
That is a description of the stimulation pattern, not a guarantee that Burst will feel better, stronger, or more comfortable for every person.
3. Modulation Mode: automatically changing rate and width
Modulation mode deliberately changes the stimulation pattern instead of keeping it repetitive.
On the technical platform underlying the Balego TENS Digital Edition, modulation automatically varies both
- Pulse width
- Pulse rate
The documented cycle lasts approximately one second. Pulse width decreases by 50% from its selected value during one half of the cycle, followed by a corresponding 50% change in pulse rate during the other half.
| Modulation Mode characteristic | Behavior |
|---|---|
| Pulse width changes | Yes |
| Pulse rate changes | Yes |
| Automatic intensity modulation | Not the defining feature |
| Cycle length | Approximately 1 second |
| Amount of programmed variation | 50% |
| Perceived pattern | Continuously changing rather than steady |
This characteristic makes modulation fundamentally different from normal.
With normal, the selected pattern stays consistent. With modulation, the unit automatically changes the pulse characteristics while treatment continues.
Why is it called modulation?
In electrotherapy, modulation simply means that some characteristic of the electrical output changes over time.
The important point is that this mode modulates pulse rate and pulse width. Other manufacturers may use the word "modulation" for different algorithms, so a mode with the same name on another TENS machine should not automatically be assumed to behave identically.
4. SD1 Mode: 40% strength-duration modulation
SD1 stands for Strength-Duration 1.
This mode works differently from ordinary modulation.
Instead of automatically varying pulse rate and pulse width together, SD1 changes intensity and pulse width in opposite directions. As one decreases, the other increases.
The documented SD1 cycle uses a 40% modulation range:
- During the first five seconds, intensity decreases by 40% while pulse width increases by 40%.
- During the next five seconds, intensity rises while pulse width decreases.
- The complete cycle lasts approximately 10 seconds.
- The cycle then repeats.
| SD1 characteristic | TENS Unit behavior |
|---|---|
| Full name | Strength-Duration 1 |
| Automatically changing parameters | Intensity + pulse width |
| Relationship | Opposite directions |
| Modulation range | 40% |
| First phase | 5 seconds |
| Second phase | 5 seconds |
| Complete cycle | 10 seconds |
The waveform diagram shows this gradual change across the 10-second cycle rather than the rapid one-second variation used by modulation.
Why does SD1 feel different from modulation?
Because a different combination of parameters is changing.
Modulation: changes pulse rate and pulse width.
SD1: changes intensity and pulse width in opposite directions.
That can produce a distinctly different sensory pattern even when electrode placement remains unchanged.
5. SD2 Mode: the larger strength-duration variation
SD2 uses the same general strength-duration concept as SD1, but with a substantially larger modulation range.
Instead of 40%, SD2 varies intensity and pulse width across a 70% range.
| Feature | SD1 | SD2 |
|---|---|---|
| Parameters varied | Intensity + pulse width | Intensity + pulse width |
| Parameters move oppositely | Yes | Yes |
| Modulation range | 40% | 70% |
| First half-cycle | 5 sec | 5 sec |
| Second half-cycle | 5 sec | 5 sec |
| Complete cycle | 10 sec | 10 sec |
| Relative programmed variation | Smaller | Larger |
SD2 therefore creates a greater change in the strength-duration relationship during each cycle.
Is SD2 simply “stronger” than SD1?
No.
The variation is larger, but that is not the same as saying that the treatment itself is universally stronger.
The actual stimulation felt through the electrodes also depends on the amplitude selected with the TENS intensity controls, electrode contact, placement, and individual sensitivity.
SD1 provides a narrower strength-duration modulation range; SD2 provides a wider one.
TENS: Normal vs. Burst vs. Modulation vs. SD1 vs. SD2
Here is the simplest technical comparison.
| Mode | Steady or changing? | Main variable | Cycle/pattern | Relative distinction |
|---|---|---|---|---|
| Normal | Steady | None automatically | Continuous | Baseline constant pattern |
| Burst | Grouped | Timing of pulse groups | 0.5–5 bursts/sec | Rhythmic clusters |
| Modulation | Changing | Pulse rate + pulse width | 1-second cycle | Rapid automatic variation |
| SD1 | Changing | Intensity + pulse width | 10-second cycle | 40% variation |
| SD2 | Changing | Intensity + pulse width | 10-second cycle | 70% variation |
The distinction between the modes is therefore primarily how the Balego TENS Digital Edition organizes and varies stimulation, rather than five different levels of power.
Why include multiple TENS patterns
A single constant electrical sensation can begin to feel familiar over time. Modes that automatically change parameters create different sensory patterns without requiring the user to continually alter the intensity controls.
Modulation is a pattern that addresses nerve accommodation by cycling stimulation intensity, while SD1 and SD2 use changing strength-duration relationships.
That does not mean one mode has been proven superior for every pain condition.
The useful distinction for the Balego user is:
- Normal = consistent
- Burst = grouped
- Modulation = changing pulse rate and width
- SD1 = moderate strength-duration variation
- SD2 = larger strength-duration variation
The mode does not determine electrode placement
Choosing Burst instead of Normal does not change where the electrodes should be placed.
Mode and electrode placement are separate parts of the TENS setup:
| Part of treatment | What it determines |
|---|---|
| Mode | Pattern of electrical stimulation |
| Intensity | Strength of stimulation on each channel |
| Pulse characteristics | Electrical timing/duration within the selected program |
| Electrode placement | Path through which current is delivered |
| Number of channels | Whether one or two complete electrode pairs are active |
| Treatment time | Duration of the session |
For body-region-specific placement, use our dedicated TENS electrode placement and settings guides instead of trying to select pad placement from the name of a mode.
How the two TENS channels work with the modes
The Balego TENS Digital Edition has two output channels.
| Setup | Electrodes | Use |
|---|---|---|
| Channel 1 or Channel 2 | 2 | One complete electrical circuit |
| Both channels | 4 | Two complete electrode circuits |
| Only 1 or 3 electrodes | Incomplete | Not an appropriate complete-channel configuration |
Each channel has its own physical amplitude control, so stimulation intensity can be adjusted independently. The selected mode defines the pulse pattern, while each channel's control determines its output amplitude.
Balego TENS versus other five-mode TENS units
| Balego-listed product | Five named modes | Main programming distinction | Best reason to consider |
|---|---|---|---|
| Balego TENS Digital Edition | Yes | Balego-branded dedicated OTC TENS platform | Straightforward dual-channel Balego TENS kit |
| TENS 7000 / InTENSity 7 | Yes | Current manufacturer documents independently adjustable pulse rate and width | Buyers specifically wanting TENS 7000 controls |
| Balego Analog TENS Unit | Different control format | Analog-style physical controls | Users who prefer direct dial operation |
| Twin Stim IV | Different program architecture | TENS + NMES | Users who also need muscle stimulation |
The key point is that the same mode name does not guarantee identical programming between brands or generations. Use the parameters that are documented for the specific machine you are operating.
For a full device-level comparison rather than another mode explanation, see Balego TENS vs. TENS 7000.
Balego TENS versus a preprogrammed “body-part” TENS machine
Some newer consumer TENS units primarily offer programs based on body region or massage sensation.
The Balego TENS takes a more technical approach by presenting stimulation patterns such as Burst, Normal, Modulation, SD1, and SD2 directly to the user.
That has an educational advantage: the mode name tells the user something about how stimulation is being delivered, rather than simply displaying a label such as “back” or “shoulder.”
Which Balego TENS mode should you use?
The safest way to answer that question is not to create a universal diagnosis-to-mode chart.
"Burst," "Normal," "Modulation," "SD1," and "SD2" describe electrical patterns. They are not diagnoses.
If a healthcare professional or current Balego instruction manual specifies a particular mode, follow that guidance.
This functional summary is more useful when learning the controls:
| If you want to identify… | Balego mode |
|---|---|
| The steady pattern | Normal |
| Pulses arranged into rhythmic groups | Burst |
| Automatic changes in pulse rate and pulse width | Modulation |
| 40% strength-duration variation | SD1 |
| 70% strength-duration variation | SD2 |
For condition-specific information, use our separate TENS settings and electrode-placement library. That prevents this mode guide from duplicating Balego's low-back, shoulder, knee, and other placement articles.
What if a new mode suddenly feels stronger?
Turn the intensity down before experimenting with a different pattern.
Even though the physical intensity control has not moved, changing pulse timing or pulse width can change how stimulation is perceived.
A practical sequence is
- Reduce both channel intensities.
- Select the desired mode.
- Confirm the electrodes remain completely adhered.
- Increase the required channel gradually.
- Stop if stimulation becomes sharp, burning, or painful.
Check the electrodes before blaming the mode
A sharp or uneven sensation is not necessarily a programming issue.
A reusable electrode that is lifting, dry, contaminated, or damaged may reduce the effective contact area and make electrical stimulation feel more concentrated. The current Balego BAL820 kit includes four reusable self-adhesive electrodes.
For replacement pads, see Balego TENS/NMES/FES Electrodes.
For a detailed explanation of pad construction, sizing, and replacement timing, use Balego's TENS Electrode Buying Guide rather than duplicating those topics here.
Frequently asked questions
What modes does the Balego TENS have?
The Balego product page presents five user-facing patterns: Constant/Normal, Burst, Modulation, SD1, and SD2. The technical manual for the identical EV-804 predicate platform likewise documents Burst, Normal, Modulation, SD1, and SD2.
Is "Constant" the same as "Normal" on the Balego TENS?
The steady stimulation pattern is referred to as “constant" or “normal.” The underlying technical manual calls this mode Normal.
What is Burst Mode on the Balego TENS?
Burst groups individual electrical pulses together rather than delivering them as one continuous evenly spaced train. The technical platform documents a 100 Hz internal burst frequency with an adjustable burst rate from 0.5 to 5 Hz.
What does modulation do?
Modulation automatically changes pulse rate and pulse width in a repeating one-second cycle on the BAL820's underlying technical platform.
What does SD1 stand for?
SD1 means Strength-Duration 1. It automatically counter-modulates stimulation intensity and pulse width across a 40% range during a 10-second cycle.
What does SD2 stand for?
SD2 is the second Strength-Duration pattern. It uses the same general relationship as SD1 but over a larger 70% modulation range.
What is the difference between SD1 and SD2?
Both vary intensity and pulse width in opposite directions. SD1 uses 40% variation, while SD2 uses 70%. Their documented complete cycles are approximately 10 seconds.
Is SD2 stronger than SD1?
Not necessarily. SD2 has a larger modulation range, but actual output sensation also depends on the selected channel intensity, electrode placement, and skin contact.
Does Burst mean low frequency?
The pulse groups occur at a relatively slow burst rate, but each burst itself contains faster individual electrical pulses. The underlying manual documents 100 Hz within the burst and 0.5–5 bursts per second.
Does changing mode change both channels?
The Balego TENS uses a common selected stimulation pattern with separate physical amplitude controls for its two channels. The intensity of each active channel can therefore be set independently.
Can I use two electrodes instead of four?
Yes. One active channel uses one complete electrode pair. Activating both channels allows four electrodes.
Is the Balego TENS an NMES or EMS unit?
No. The Balego TENS Digital Edition BAL820 is a dedicated TENS device. Customers who also require muscle stimulation should compare a TENS/NMES combination device instead.
Is the Balego TENS FDA cleared?
Yes. The Balego TENS Digital Edition with Accessories for Pain Relief received FDA 510(k) clearance under K181207 as an OTC Class II transcutaneous electrical nerve stimulator.
What is the BAL820 cleared to be used for?
Its cleared OTC indication is temporary relief of pain from sore and aching muscles in the low back and upper or lower extremities caused by strain from exercise or normal household and work activities.
Where can I buy the Balego TENS?
See the Balego TENS Digital Edition for current kit contents, pricing, replacement accessory links, and availability.
Safety notice: The Balego TENS is intended for symptomatic temporary pain relief within its labeled OTC indication; it does not diagnose or cure the underlying cause of pain. Read the current BAL820 instructions before use, follow permitted electrode-placement guidance and reduce intensity before changing pads or stimulation settings.
