Systems that provide electronic transmission of ordinary documents, including drawings, photographs, and maps. The original document is scanned at the sending station, converted into an analogue or digital representation, and sent over a communication channel to the receiving station, which constructs a duplicate image on paper; this image is referred to as a facsimile. Early facsimile systems were exclusively analogue, but modern systems use digital techniques for data encoding and transmission. Commercial facsimile services are known as fax.