| 摘要 |
A pager is provided with a differentiator circuit and an integrator or a comparator circuit. The differentiator circuit turns received four-value analog signals into signal level variations. In a construction with an integrator circuit, the signal level variations are integrated and expanded to become pulse signals having widths proportional to the signal level variations. The levels of the pulse signals are determined according to the directions of the signal level variations. Four values are distinguished based on a known value of a synchronizing signal and the levels and widths of the pulse signals. In a construction with a comparator circuit, the signal level variations are compared with six reference levels and classified into seven classes by the comparator circuit, so that four values are distinguished based on the known value of the synchronizing signal and the classified level variations.
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