Line level   

Line level signals are commonly used for sending audio from one device to another. Patch cords usually carry a line level signal. Line level is defined as any signal above 25 millivolts RMS. Professional devices  at  0 dB VU meter output  +4 dbm or 1.228 volts RMS 9600 ohms impedance). Domestic or home entertainment devices (CD players, cassette decks, etc.) and semi professional studio devices will use a -10 dB signal in 10,000 ohms impedance which has considerable less gain (.5 volts).
Devices designed for electric guitar signals are designed to face an even higher impedance (100,000 ohms +) and may output a wide array of line level values.