This tone generator is ideally suited to electronics testing, electrical, construction and building maintenance. Alligator clips connect the device to non-terminated cables, while the RJ11 and RJ45 modular connectors work with telephone and internet wiring. Insulated inductive probe protects cables under test from shorting. Built-in speaker with adjustable volume/sensitivity and tone selection between "continuous" and "wobble" lets you hear if you've found the right cable or identify breaks. Green, yellow and red LEDs light up steadily, flicker, or dim and brighten in response to different wiring conditions and tests.