The Rolls PM57 is for connecting headphones to a speaker line. The 1/4" Mono/stereo loop jacks are for connecting many boxes in series. There are 2 headphone jacks and volume control. The PM57 uses the speaker line signal for power and uses no batteries. The attenuation switch on the PM57 helps match the correct level input to get the desired headphone level.
|Input Impedance||150 ohms|
|Dimensions||2.75" x 3" x 1.25" / 6.98 x 7.62 x 3.17 cm|
|Weight||0.5 lbs / 0.22 kg|