Image Number 5 for United States Patent #5369799.
A radio pager has a variable gain adjustable to high setting for normal reception or low setting at which the strength of intermodulation products is reduced in relation to the strength of a desired signal. A sync code contained in a received signal is detected to establish synchronization and a sync-absence signal is generated if it is not detected during a time interval in which it is expected to occur. The pager is initially switched to the high gain setting. In response to a first generation of the sync-absence signal, the pager recognizes that the desired signal is severely affected by intermodulation products and switches to the low gain setting so that the signal-to-noise ratio of the desired signal is improved. In response to a second generation of the sync-absence signal, the pager recognizes that its amplification gain is not sufficient and switches to the high gain setting to resume normal reception.