The word attenuverter, a combination of attenuator and inverter, has become pretty standard in the modular synth world. The attenuverter does exactly what it's name suggests: it is a single control that can be used to attenuate and optionally invert a signal. Turn the control clockwise to get an attenuated version of the input signal, and counter-clockwise to get the inverted version. With the control at center position, the output is simply off.
Attenuverters are great for flexible modulation routing. However, it is this center position where they can be very annoying: it can be difficult to dial in a small amount of modulation. Turn it down too far, and you end up increasing it again on the inverting side.
The precision attenuverter is designed to help with this problem. By adding load resistors to the potentiometer, the response curve is made non-linear, increasing the sensitivity near the center.
