Closed Loop Lock (Lux's naming)
This is an improved system of AFC circuit. Here the loop gain is large, because the varactor is controlled by DC amplification and bandwidth regulation of DC components in FM detector, and therefore it is possible to strongly lock the local oscillation frequency to that of broadcast station. Because of the bandwidth regulation, and adjacent station cannot be pulled in. The locking circuit operates even when the station has a smaller digit of frequency such as 88.125MHz. The naming of similar circuits differs from one manufacturer to another.