| 摘要 |
In a selective call radio receiver for receiving a radio communication signal to produce a communication datum of a multiplicity, such as 256, of levels and an intermittent succession of synchronization patterns, a combination of a pattern detector, a sample memory, and a threshold calculator detects a predetermined number, such as three, of detected threshold levels in each synchronization pattern. A threshold memory stores first to N-th past sets of stored threshold levels, N being equal to two or greater. Based on a current set of the detected threshold levels and the past sets, a threshold comparator generates optimum threshold levels for use in a discriminator for judging the communication datum as a multilevel, such as four-level, receiver output signal. Preferably, operation of the receiver is suspended when the detected threshold levels are abnormal, when the current and the past sets are not spaced apart by a synchronization interval, or when the optimum threshold levels are not within allowable ranges therefor.
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