Decoding facsimile data from the Rapicom 450

This note describes the implementation of a program to decode facsimile data from the Rapicom 450 facsimile (fax) machine into an ordinary bitmap. This bitmap can then be displayed on other devices or edited and then encoded back into the Rapicom 450 format. In order to do this, it was necessary to understand the how the encoding/decoding process works within the fax machine and to duplicate that process in a program. This algorithm is descibed in an article by Weber [1] as well as in a memo by Mills [2], however, more information than is presented in these papers is necessary to successfully decode the data.