Universal Bass Knob</br>Built in Voltage Meter</br>Built in On/ Off Switch</br></br>Product Description</br></br>Features Digital Volt Meter 10.0v - 15.9v Pushable On-Off Switch Turn Amplifier On and Off Blue LED Display High Voltage | Low Voltage | Protect Remote Gain Control</br><br/>http://www.amazon.com/gp/product/B01LZ63DXP