ATP-Series of attenuators allows the output level of a network of 25V or 70V speakers to be controlled from a wall-mounted volume control, without affecting overall amplifier volume settings. A bypass function overrides the volume control knob setting when activated by 9V to 30V DC. Applying 9V to 30V DC between pins labeled D+ and D- bypasses the volume control function and provides full volume audio to the speakers. The ATP-Series attenuators feature etched faceplate markings.