| 摘要 |
PURPOSE:To prevent a malfunction in case the receiving electric field drops extremely, by providing a Q signal level detecting circuit to detect whether the output level of a Q signal wave detecting circuit is lower or higher than the reference level and then to control ON/OFF of the output of a control signal discriminating circuit which is supplied to a matrix circuit. CONSTITUTION:The output of a Q signal wave detecting circuit 7 is connected to a control signal discriminating circuit 8 and a Q signal level detecting circuit 13. The circuit 13 rectifies the output of a Q signal wave detecting circuit 7, detects the Q signal level on the basis of the DC level and produces a switch signal to turn on and off a switch circuit 12 when the DC level is normal and exceeds the reference level, respectively. The output of the circuit 13 is kept at a fixed level in a normal receiving state. The circuit 12 is turned off in case the receiving electric field drops extremely and the noises increase extraordinarily. This process prevents a malfunction of a matrix 10 due to a control signal which is erroneously detected. |
