The FP-PA18 and FP-PA18H are high efficiency 18 W power amplifiers with a line input, 8 ohm output and an integral audio compressor. The FP-PA18 circuits are all designed for low power consumption. In the absence of an audio input, a digital timer is enabled to switch the class D output stage off. When this sleep mode is active, the amplifier module and its included RDL power supply consume less than 1 W of mains power. Both models feature a balanced line level input that may be connected unbalanced. The output drives one 8 ohm speaker or multiple speakers connected to present an 8 ohm load to the amplifier. The output stage of both models includes an audio detector that illuminates the green OUTPUT ACTIVE LED and provides an active open collector output when amplified audio is present at the module output. This output is useful to control other equipment or to verify amplifier operation using high or low frequency low-level test tones.