The CWF/EWF Series are small, lightweight, economical type optical data transmission devices that enable data to be transmitted quickly and reliably between an aligned pair of units over mid- range distances. Typical uses are on overhead and stacker cranes, automated storage and retrieval systems (AS/RS) and transfer cars for non-contact bi-directional communication from the vehicle to the control unit. The use of modulated light as the transfer method means that these transceivers do not incur physical wear like trailing cables and slip rings nor do they require recalibration like radio systems.