Phone line testers are special devices used to install, test, and evaluate the quality of a phone line. These gadgets have a speaker and a microphone, a keypad, and a number of leads that are used to connect a line tester to a phone wire. Such gadgets are connected to distribution frames or any other interface areas that provide access to phone lines. When plugged in, these gadgets gain the functionality of a regular phone, so the technician has the ability to monitor any ongoing calls, make outgoing calls or answer incoming calls. With this device, you can also pinpoint phone lines and check dial tones.