The Touch Tester is an "on demand" wrist strap tester that also functions as a common-point ground for two wrist straps and a mat. When the wearer of a wrist strap touches the metallic surface of the Touch Tester, a path for current flow is completed from the wearer's skin, through the wrist strap, to the metallic surface to ground. This action will cause the green "test good" LED to light (and the optional audible signal to sound) as long as the resistance of the circuit path is between 750 kilohms and 10 megohms.
The wrist strap being tested may be plugged directly to the tester or any convenient common ground point. The wrist strap will test properly as long as both the Touch Tester and the wrist strap are connected to a common ground. Therefore, any number of wrist strap wearers may use the Touch Tester if they can conveniently reach it. Desco item 09740 provides two banana jacks for grounding wrist straps.
When the Touch Tester and a 09740 are tied to a common ground (utility ground) wrist straps plugged into the 09740 can also be tested.