The NS-2 can be connected in two different ways. You can connect the NS-2 last in your chain of effects. The output of the previous pedal goes to the NS-2 input jack. Wire the Output jack of the NS-2 to your amp. The NS-2 can also be wired like an effects loop, which allows you to kill your entire signal chain just by stomping on the NS-2. Take the Send output of the NS-2 into your first pedal. Take the output of your last pedal and wire it to the Return jack of the NS-2.
The NS-2 uses an intelligent circuit to differentiate between the sound of the guitar and noise. The NF-1 simply cut all sound when it became weaker than a threshold value. The NS-2 attempts to let the sound of the guitar through while re-moving the noise