http://www.ultimate-guitar.com/forum/showthread.php?t=1288038

여기의 포스트가 그나마 킬스위치의 원리를 가장 잘 설명해놓은 듯하여

퍼온다..

요점은 아웃풋에 신호가 빠지는 부분을 끊으면(스위치를 누르면)

파핑노이즈가 생기는데

신호선을 그라운드에 붙여주면 (스위치를 통해서 신호가 타면)

볼륨 포트와 스위치의 저항차이에 의해서 (이건 아래 글에는 없다)

아웃풋에서 빨간선으로 신호가 빠지지 않고, 스위치를 타고

그라운드로만 신호가 빠져서 킬 효과를 줄수 있다는 것...

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2."How will it work?" Alright, so we now have a goal. We want the signal to remain as-is when the switch isn't being activated. When the switch is engaged, no signal whatsoever is to get to the tip of the jack/ hot output.

So how are we going to do that? There's 2 simple ways.
one way, and what would seem like the most obvious way, is to break the connection between the guitar's output and the jack using a switch.
basically, we want this to happen when we press the switch:

In a perfect world, this would work just fine. we're stopping the signal from the pickups from getting to the hot output, and we'd hear nothing when the switch is engaged.
Unfortunately, we don't live in a perfect world. Just because we stop the pickup's signal from getting to the hot output, doesn't mean we're stopping all signals from getting there.
Computers, phones, TVs, the wiring in your house, microwaves, and pretty much anything electrical you can think of, all give off EMI (electromagnetic interference) / RF interference (radio frequency interference). an extreme example can be heard when you play guitar in front of your computer, or if you get a phone call while your cell phone is on top of your amp.

If you wire a killswitch to simply disconnect the guitar's output from the jack, you're still leaving the tip of the jack wide open to receive static and hum caused by interfering signals.
If you turn on your amp, plug a patch cord into it, and leave the other end of the cable unplugged, you'll hear the same amount of hiss and noise.

note that in some areas, this may not seem like a big deal. your basement might be relatively quiet in terms of RFI, but playing in different rooms of your house could give you different results. You definitely don't want to use this kind of killswitch if you're on a stage underneath a bunch of bar lights and fluorescent neon beer signs..

So now we know that cutting off the output from the guitar doesn't actually mean we're left with a completely silent output. so what do we do?
remember how the sleeve of the jack is grounded? well, if we connect the hot output to ground, theres no way a signal can be present

So now, when we press the switch, we want this to happen:

connecting 2 points electrically is essentially making them the same point, and a voltage (signal) is apparent only when there's a potential difference between 2 points. the signal used to be between the tip and sleeve of the jack, but if they're the same point (both grounded), there can be no signal. not from the pickups; not from anywhere.

The only issue some people may have with this wiring scheme, is that there's sometimes a 'pop' noise when you switch from the normal signal, to 'killed' position. the solution for that is a very high value (very high resistance) resistor across the terminals of the switch. We'll go into greater detail on that in the wiring section.

What's important now is that we have an idea of what we want to happen when the switch is activated. We want to short the output to ground.