On a narrow conveyor section, transparent objects or containers being conveyed in sequence have to be detected with positional accuracy and a short response time to trigger their labeling. The compact retro reflective sensors of the O-30 series are particularly suited for economical detection of transparent objects on a narrow conveyor section. The sensor is extremely fast, featuring a switching frequency of 2000 Hz, which makes it ideally suited for high-performance labeling machines. It is easily operated using a potentiometer and NO/NC switch.