| 摘要 |
An automatic gain control 20 is adapted to compensate to equalise the gain for signals of different characteristics (e.g. the preamble region and the main data region of a signal retrieved from a tape). The signals are amplified by a VGA 32, the output of which is monitored by a peak detector 44, whose output is compared at amplifier 48 with a respective target value for the particular signal region from a associated counter or register 60, 62, 65, to control the gain control signal applied to the VGA 32 by a gain control 50. The output of the comparator amplifier 48 is monitored before and after the transition between the first and second signal regions and the reference values in the appropriate register 60, 62 incremented or decremented in accordance with any step in the output of the amplifier 48, substantially to equalise the gain before and after the transition. <IMAGE> <IMAGE> |
