This technical report describes a three layer data exchange architecture used for communication with large industrial and commercial customers' metering equipment (aiming, in particular, at the remote reading of these meters for billing purposes). The public switched telephone network (PSTN) is used as a communication medium for this data exchange. This technical report defines the protocols to be applied for each layer of the architecture (physical, data link and application), making use as far as possible of existing standards, such as – ITU-T V.22, V.22bis, V.23, V.24, V.25, V.25bis, V.28, V.32, V.32bis and V.41 (ITU-T: telecommunication standardization sector of the International Telecommunication Union), – IEC 61334-4-41 which describes the DLMS (Distribution Line Message Specification) model.