Step control solution for compressor capacity can
be achieved by using a step controller EKC 331 À.
EKC 331 is a four-step controller with up to four
relay outputs. It controls the loading/unloading
of the compressors/pistons or the electric motor
of the compressor according to the suction
pressure signal from the pressure transmitter AKS
33 Á or AKS 32R. Based on a neutral zone control,
EKC 331 can control a pack system with up to four
equally sized compressor steps or alternatively
two capacity controlled compressors (each
having one unload valve).
EKC 331T version can accept a signal from a
PT 1000 temperature sensor, which may be
necessary for secondary systems.
Neutral Zone Control
A neutral zone is set around the reference value,
***in which no loading/unloading occurs.

Касательно последнего предложения: сомневаюсь к чему относится "in which" - к neutral zone или к reference value.
И буду благодарна за хотя бы прибл. перевод этого предложения.

Спасибо!

A neutral zone, in which no loading/unloading occurs, ...