What do the input conditions that are specified in the catalog for "voltage input" mean?

Voltage Input

Example: Using an H7E[]-NV

High (logic) level: 4.5 to 30 VDC

Low (logic) level: 0 to 2 VDC (input impedance: approx. 4.7 kΩ)

High (Logic) Level

This refers to the voltage level at which an input turns ON. If a voltage of 4.5 VDC or higher is applied as a voltage input signal across terminals 1 and 2 for the count input and across terminals 3 and 4 for the reset input, the voltage can be read as an input signal.

Low (Logic) Level

This refers to the voltage level at which an input turns OFF. When the input is a two-wire input or an SSR (Solid State Relay), the leakage current when the input is OFF will cause residual voltage across terminals 1 and 2 for the count input and across terminals 3 and 4 for the reset input.

A voltage of 2 V or lower is detected as an OFF signal.