Another type of demodulator, the product detector, can provide better-quality demodulation with additional circuit complexity. V. An example is the X demodulator used in the X/Z demodulation system. A multi-loop modulator/demodulator feedback approach was used to generate an accurate arcsin signal. The cable tuner, QAM demodulator, and MPEG decoder are part of the host equipment. The demodulator extracts the audio or other modulation from the IF radio frequency. Significant conditions are recognized by an appropriate device called a receiver, demodulator, or decoder. After passing through the communication channel the signal is decoded by a demodulator. The exact structure of the demodulator is defined by a modulation type. The product demodulator has some advantages over an envelope detector for AM signal reception. Some systems used a demodulator to decode discrete sound channels. A product detector is a type of demodulator used for AM and SSB signals. Metal rectifiers were also used as envelope detector (AM demodulator) diodes in radio receivers. Sometimes a digital automatic gain control circuit is implemented in the demodulator. These receivers include a photo-diode, an automatic gain control (AGC) circuit, and a demodulator. There are also additional components in the demodulator such as the Intersymbol interference equalizer.