SICK GRTB18-P1117 Photoelectric sensors. SICK GRTB18-P1117 is a photoelectric sensors in the GR18 family. SICK identifies this exact configuration as manufacturer article 1076114. The official technical record specifies Functional principle: Photoelectric proximity sensor; Functional principle detail: Background suppression; Dimensions (W x H x D): 18 mm x 18 mm x 71.5 mm; Housing design (light emission): Cylindrical; Thread diameter (housing): M18 x 1; Optical axis: Axial. The linked SICK data sheet is specific to GRTB18-P1117.