SED, SCD, SPD, SSD, and XRD type optical detectors are for use with the ILT1700, ILT2400 and ILT5000 Radiometers.“SED” specifies detector housing style and meter connection (again SEL, SCL, SPL, SSL, and XRL detectors have been discontinued; SED, SCD, SPD, SPM, SSD, and XRD type detectors are for use with ILT2400, ILT5000, ILT1700 Radiometers).