Ground Gard, Dual Operator, 5.5 Monitor with Buzzer, Switch, 120V
Per The ESD Association ESD TR 12-01 "Survey of Constant (Continuous) Monitors for Wrist Straps": "Since people are one of the greatest sources of static electricity and ESD, proper grounding is paramount. One of the most common ways to ground people is with a wrist strap. Ensuring that wrist straps are functional and are connected to people and ground is a continuous task."
Capacitance (or single wire) constant monitors: "The monitor circuit sends out a signal through the wrist strap that changes because of the person to ground capacitance. The monitor then detects this change to determine that a person and ground are present. If the electrical connection to the person (wrist strap), or to ground (grounding wire) should open (become disconnected), the circuit will go into the alarm state."