EW shift SOP addition:
This section details how things work if only special sensors are involved.
Nothing happens here- no damage modifiers
Count the number of special sensors on that side (if a scout has Enhanced Sensors (D5.60), double their count). If they have more than 5 sensors, truncate the result to 5. They may increase their damage by x% or reduce the other side's damage by x% (you can't split it, it must be the full x%) where x is the sensor count.
Example: The UFP has a SC in their force. Its 8 special sensors would be reduced to 5 for this battle (too much of a good thing...).
Count the number of special sensors on each side. Make sure to adjust the count for any scouts with Enhanced Sensors (D5.60). Take the difference of the two numbers, and use this value (again, truncate to 5 if it is larger). As before, you can adjust the damage by that percentage (increase yours, decrease theirs).
Example: The UFP has a SC, the Klingons have a F5S (2 special sensors). The net result is 6, truncated to 5% in the UFP's favor.
Follow the above process, but instead of truncating to 5%, do so to 6% (SA-I), 7% (SA-II), or 8% (SA-III).
Example: The UFP has a SC, the Klingons have a +F5S (2 special sensors, with ESS so treated as 4). The net result is 4, 4% in the UFP's favor.
Follow the process yet again. If the side with the lower sensor count has AAP, reduce the net shift by 4%.
Example: The UFP has a +SC against the Klingon's +++D6S. The UFP has SA-III tech as well, The net shift is 8%, which is reduced to 4% due to AAP. If the UFP didn't have any levels of SA tech, the shift would be 5%, and the AAP shift would make it 1%. If the battle were more closely matched (+SC vs. +++D6S and +F5S plus a F5S), then the result would be 16 vs. 8 + 4 + 2 or 2, and AAP would nullify the remaining 2% shift.
Follow the above process, but evaluate the ESM's special attack's effects first. In this example we are using "b" which gives it a 50% chance to reduce the sensor count of an ESS scout by 50% (i.e., basically you ignore the doubled sensor count that ESS provides). If the target is an AAP scout, it'd lose the 4% shift feature provided by AAP plus the sensor count doubling from ESS.
Example: The UFP has a +SC and a GSC with ESM. They are up against the Klingon's +++D6S, a 2nd +++D6S, and an +F5S. If the GSC's neutralization attack fails, you've got 16 + 8 vs. 8 + 8 + 4 (net 4% to the UFP) and the Klingons reduce that to 0% via AAP. If the ESM neutralization works, you've got 16 + 8 vs. 4 + 8 + 4 (net 8% to the UFP since they presumably also have SA-III). The +++D6S that didn't get neutralized would be able to use AAP and reduce the shift to 4%.
Example: The UFP has two +SC and a GSC with ESM. They are up against the Klingon's +++D6S, +D6S, and an +F5S. In this case, there is only one AAP scout to target on the Klingon side to worry about (and we target it). If the neutralization fails, you've got 16 + 16 + 8 vs. 8 + 8 + 4 (net 20% to the Feds, truncated to 8% since they presumably have SA-III). AAP reduces that further to only 4%. If the neutralization worked, you'd have 16 + 16 + 8 vs 4 + 8 + 4 (24% to the Feds, truncated to 8%).
Follow the above process. Note that things could get interesting depending upon how the dice fall (neutralizing a large sensor count unit with AAP or ESS could change the balance, for example). Note that ESM attacks are simultaneous, so it is possible that UFP's GSC with ESM could be neutralized by a D6S with ESM but also neutralize it in turn).
In this section, no one has special sensors, just SFGs.
Nothing happens here- no damage modifiers
Per (F4.60d), you may have up to four SFGs on a side (note that this is SFG count, not units with SFGs nor "SSD boxes per SFG", so a B10AA would count as two while a D7A would count as one). Typically the shift is 2%/SFG (empires with knock off versions would typically only get 1%/SFG). Like special sensors, you can use this shift either to up your damage or lower the other side's damage.
Note that in the rare case that both sides have SFGs, they each get to shift the damage (vs. the special sensor case where you only get the net sensor count).
Example: A B10AA force is facing off against a FRAX force (which has the 1% style SFGs). Both sides have 4 SFGs. Depending upon how the two sides decide to allocate the effects, there could be a 8% damage adjustment vs. a 4% one (both sides pick different sides to impact), or a net 4% damage adjustment (the FRAX cancel out half the Klingon's SFGs after they target the same side).
Per (T5.120b), the SFG effect is halved (round fractions up).
Example: The FRAX have a single SFG that targets a Romulan force that is protected by HS-II. The FRAX's 1% is halved (but rounds back to 1% anyway).
SFG and special sensors shift the damage % independently. This means shifts may apply to/from both sides depending upon who has what.
SFG vs. SS- Since each SFG allows a 2% shift (1% for knock off models), with up to 4 per side allowed, you may have up to an 8% shift (either increasing your damage or decreasing the other side's). The side with more special sensors (5; up to 8 if they have SA-III tech) this also allows an up to 8% shift. If the two types of damage adjustment belong to different sides, you may have no shift (due to canceling each other out), minimal shift (if the SFG vs. SS numbers are not the same strength), or a shift to each side.
Example: Both sides have SA-III tech. The Klingons have a B10AA, C9A, and a D7A (4 SFG in total, spread across 3 ships). They also have several scouts. Opposing them are the UFP who have a number of scouts. Once the numbers are compared, the UFP has a net surplus of 8 special sensors. The Klingons may increase their damage by 8% (or reduce the UFP's by that 8%) due to their SFGs. The UFP can do the same 8% shift due to their special sensor superiority. Both sides decide this simultaneously. This means that you can end up with a net 0% shift (they both try to affect the same side), a -8% to each side (they target the other side for reduction), or a +8% to each side (the Klingons use their SFGs to boost their damage by 8%, the UFP uses its EW superiority to increase their damage by 8%).
If one side has both a SS advantage and SFGs, there are two different shifts available. They can be stacked or applied to different sides.
Example: The Klingons have a B10AA, C9A, and a D7A (4 SFG in total). They have destroyed or captured enough UFP scouts to result in the Klingons having 7 more sensors than the UFP. They can stack the two results (so +15% damage to the Klingons or -15% damage to the UFP), or split them (+8% or +7% to the Klingon's damage and -7% or -8% to the UFP's).
While rare, you could have both sides with SFGs. This would result in up to three shifts (side A and side B have a SFG shift and one has a SS related shift).
Example: The Klingons have their usual SFG ships and are facing off against the FRAX (who also have 4 SFGs, albeit the 1% types). There would then be a 8% shift from the Klingons, a 4% from the FRAX, and whatever the special sensor shift is.
SFG, SS, AAP, and ESM can stack and make things even more confusing. It follows the examples already provided, however.
Example: The Klingons are assaulting Sol in preparation for annihilating it (see F6.52). To this end, they have two squadrons, each with a B10AA, D6S (with AAP and ESM), and assorted other scouts (plus lots of other, not relevant SQs that have been AMed together via (C2.60)). The UFP has assorted scouts of their own (equal SS count), including two GSC with AAP and ESM (also lots of other not relevant SQs AMed together and some bases). Both sides have SA-III tech. Presumably, each D6S will use their (D5.91b) ability to target a different GSC (all the SC hulls have long since been lost in combat, otherwise neutralizing those would have the best bang for the buck due to their higher sensor count (8 for the SC vs. 4 for the GSC)). Each GSC will do the same to a different D6S. Depending upon how the dice fall, the EW situation could favor either side (or neither). The Klingons will always have an 8% shift available due to their SFGs.
In some cases (the Random Maneuvers RX (C2.120) and the Legendary Base Commander (D11.30b) being the most common ways) someone's battle intensity might be reduced which in turn reduces the amount of damage they can do. A player might use their SFG/EW shift(s) to compensate. Or, if the other side has a downshifted BI and you have the advantage, you might further kneecap their damage potential (with a -8% shift, Regroup and Evasion will sometimes do no damage at all, and even if they do some, it'll at most be half of what it'd normally be).