Another Sinclair Radionics product that was introduced in 1964 and failed was the first class D amplifier kit rated at 10 watt RMS: a class D switching amplifier that was good in theory but sadly ahead of its time and available technology. The amplifier used low-frequency germanium transistors as pulse width modulators and switches and wrongly relied on the loudspeaker's inductance to filter the class D signal into audio. Most often this would short out the output transistors. When it did work the power level was far below 10 watts and Sinclair's main advertising channel, "Wireless World" magazine, was so deluged with complaints that it supposedly refused to take further advertisements from Sinclair.