A sensor attachment device is provided for attaching a sensor device in such a way that removal of the sensor device without damage is ruled out, whereby the sensor device has a pair of holding fingers and a pin. The device is designed to take the place of open style adapters and connectors. Headwall units having water dispensers are also disclosed. Non-volatile memory stores control voltages during operation in other embodiments to relax the area requirements otherwise required for integration capacitors to store phase and frequency information. A candidate text line classifier is applied to further screen out false-positive text identifications. Each mirror of each array is movable to target any selected mirror of the opposing array.