Patlite WDT-4LR-Z2 Instruction Manual page 25

(1-2) Distance Between Devices
 Place the WDT within a 20 m radius (recommended line-of-site distance) of the WDR.
 If more distance is required, add another WDT.
(1-3) Ensuring Line of Sight
 Good line of sight for each device (WDR, WDT) and free of any obstacles hereafter referred to as the Fresnel Zone - is
required. The Fresnel zone is a three-dimensional space, whose size is estimated as follows:
If you cannot set up the Fresnel zone, sometimes the available communication distance may be shorter than
usual due to obstacles inhibiting communication.
 When installing on a metal plate or concrete wall, install the devices in the Fresnel zone so they are free of any obstacles.
Line of sight L: 20 m ⇒ Fresnel zone diameter D: about 1.6 m
Line of sight L: 10 m ⇒ Fresnel zone diameter D: about 1.2 m
Wireless Data Acquisition System Instruction Manual
25