| 摘要 |
PURPOSE:To attain the operation of efficient data communication by feeding back an output signal of a differentiation circuit to a peak value automatic gain amplifier circuit as a gain controlling signal by means of a simple additional circuit even if there exists level sudden change of transmission line or noise. CONSTITUTION:If a level drop phenomenon due to sudden change in level of the transmission line occurs in an input signal A, no output signal DET is formed. But a signal where an output signal C of a multi-level detecting circuit 31 becomes a reference level or below of the circuit 31 in response to the input signal A is detected, given to an AND circuit 32 and an output signal D is formed. This signal D is differentiated by a differentiating circuit 20 to form an output signal B'. This signal B' is impressed to a smoothing circuit 17 to clear an output signal E of the smoothing circuit 17 before level sudden change and a demodulated input signal after level sudden change is restored as an output signal OUT12 of an AGC circuit 13. Further, even if a noise is mixed in the input signal of the demodulating circuit and a receiving signal detecting circuit 19 is not operated, the multi-level detecting circuit 31 is operated and the received input signal is restored. |
