This document is an instruction manual for the 504910 digital transmitter, including warranty, preliminary examination, general description, functional description, specifications, installation, calibration mode, setup mode, measure mode, errors, pH/ORP probe check, temperature compensation, last calibration data, offset and slope direct selection, event log file scrolling, fault conditions, RS485 communication, modem connection, self-test procedures, pH values at various temperatures, electrode conditioning and maintenance, accessories, and CE declaration of conformity.