system
Given the following post, respond as if you're commenting on Reddit:
human
[The Culture] What are Effectors exactly?

In the Culture novels effectors show up a lot, but it's hard to get a read on their limits. They seem to be able to be used for surveillance, or just mucking around with things.'

Are we ever given a scientific explanation for how they work, or what their limits are?
gpt
Effectors are electromagnetic manipulators. They can basically do anything with the electromagnetic spectrum to an extent and from a range dependent on the strength of the effector. This means they can send and receive the entire spectrum of electromagnetic radiation, read minds, able to manipulate electronics, insert thoughts, excite nerves, or just plain dump energy into something if they wish. Basically, if anything involves electrons or electromagnetic waves and would be affected by manipulating it, the effector can probably do it. They work through hyperspace, which circumvents normal lightspeed restrictions. 

Effectors are limited in that they have not been shown to work on chemical/mechanical weaponry, though it is more plausible that this is due to the lack of EM waves they produce - if the Culture ship could determine the presence and positioning of said weaponry through other means, there is nothing to stop an effector from wasting them either. So in a sense, the real limitation here is that effectors cannot sense non-electronic weaponry, and it would certainly be more inefficient than frying a wire or two.

Effectors can also be blocked by 4D shielding. Even this can be forced through; however, the ship is extremely wary of this due to the difficulty of hyperspace calculation causing collateral damage: 

"Once the ship's back, in about twelve minutes, we have the option of blasting the shielding out of the way and Displacing in, but that's a last resort; wasting 4D without causing horrendous collateral in the associate flat-space is almost impossible. In 4D you think all you've done is kick down a door, and imagine you've done it really neatly, minimum force, but then you look back into 3D and realize you've blown down the whole building. Sometimes the whole block."

The other counter to effectors is simply using your own effectors. It flips one bit, your effector senses it and flips it back. It ramps an electron's energy state up, you slap it back down. That's how equiv-tech fights go until one ship screws up and ends up turning against itself and its allies.

The limits are based on the strength and number of the effectors and the ship's imagination and skill more than anything else.