This device is a 50 watt dummy load with a headphone output jack.The headphone jack is a stereo jack wired for mono operation. The output level to the headphones is continuously adjustable. A variable line out is also provided. The load switch switches between the normal speaker for the amplifier and the internal dummy load, which is nominally 8 ohms. Most amplifiers will tolerate a 2 to 1 impedance mismatch. The headphone output jack and its volume control are always active regardless of the position of the load switch.