Abstract: A detector arrangement for a data-card reader is capable of reading both punched cards as well as cards marked in writing. A light source emits light in the direction of the data-card surface, and a detector receives the light reflected from said direction and delivers an output signal in response to the intensity of such light. A surface having a reflective power higher than that of the card material is provided at the back of the data-card in essentially parallel relation to the latter. A high-level output signal is obtained when a hole in the card is detected. A medium level is obtained when there is no marking on the card, and a low level is obtained when a pencil mark is encountered on the card.