S2222: Wrist Strap Monitoring System for 2-Operator The S2222, is a small & precise device for constant monitoring of 2 standard single conductor wrist grounding straps, with audible & visible alarm features. NIST Certified. Product Information Related S2221 Wrist Strap Monitoring System for Single Operator S2771 Workstation Monitoring System S2772 Workstation Monitoring System S2555 Single-Wrist Strap & Mat Ground Monitoring System SM2 Resistive-Base Dual Workstation Monitoring System