There are two types of Modulation-Dependent Carrier Level (MDCL) control methods: DCC, as discussed above, and Amplitude Modulation Companding (AMC), developed by the BBC. The AMC design achieves the opposite effect of the original DCC system: the carrier is at maximum when no audio is present, and is reduced by up to 75% when the audio is loudest. The system uses the carrier to quieten the channel when no audio is present, while still realizing power savings. Both DCC and AMC have been a staple in European MW broadcasting for many years, and now AMC is now being used by stations in North America.