Cable Testing: 1. At first, turn the rotary switch fully clockwise to test the battery strength. The battery LED will light bright green if the internal battery is fully charged. 2. Then plug one end of the cable into the appropriate jack on the left side panel of the cable tester, Plug the other end of the cable into the appropriate jack on the right side panel. Set the rotary switch to "1" to test the connection of contact 1 on the plug inserted into the left side panel. 3. lf there is a connection, the Green LED will light below "1" and a Yellow LED will light above each contact on the right side plug connected to "1" on the left side plug. Use the charts below to verify proper cable connections. 4. If no LED lights than there is no connection and the left side contact "1"is "floating" due to design or an "open" in the cable. Set the rotary switch to "2" to test contact 2, and so on, until all contact shave been checked. 5. If the Ground LED lights than there is a connection between the corresponding contacts and the chassis. To test the cable with a banana plug, just plug each end of the cable into the banana jacks. The LED will light and the unit will beep a tone if there is a connection between the plugs. These banana jacks can also be used for continuity tests using two probe leads. CT-20C Cable Tester. 16-in-1 cables checker, 10-way Switch Wire Tracker with LED Indicators. Can test cables with Type-C, USB, HDTV, DIN, RCA, RJ45, 6.35JACK, 3.5JACK, XLR, Speakon... Color: As Shown Material: Metal Package Contents: 1 * CT-20C cable tester (without 1 x 9V battery)