Lainejuhi piirsagedus on madalaim sagedus, millega konkreetne elektromagnetlaine saab selles režiimis levida. Sellest sagedusest madalamal nõrgenevad signaalid oluliselt.
The cut-off frequency of a waveguide is the lowest frequency at which a specific electromagnetic wave mode can propagate through it. Below this frequency, signals are severely attenuated.