<p>In a knock control system which has a knock control unit constructed of a transducer portion (1) for detecting vibrations of an engine and converting them into an electric signal and a knock signal processing circuit unit (44) for delivering a signal expressive of the occurrence of knock on the basis of a knock signal from the transducer portion, and which controls the ignition timing of the internal combustion engine on the basis of the knock signal from the knock control unit; the improvement comprising the fact that at least either of the transducer portion (1) and the knock signal processing circuit unit of the knock control unit (44) is mounted on a part of a distributor which has a fixing base portion (40) at a part of a housing thereof. </p>
