Abstract: In a control circuit, which has a current switching-over circuit including at least four switching transistors for controlling a current flowing through an electromagnetic device, the control circuit has driving circuits each of which drives the switching transistors in such a way that a short circuit does not occur during the switching-over operation thereof.

Abstract: A driving circuit for use in controlling a motor for controlling an air mixing door, an inner and surrounding air change-over door and a mode setting door and the like used in a vehicle air conditioning device, or a motor used in opening or closing of window panes of a vehicle or in opening or closing the door which includes a control transistor for use in controlling a transistor circuit having a transistor to cause both normal and reverse directed currents to flow in a vehicle motor, the control transistor being operated until a specified period of time has elapsed after the power supply switch is turned on, the motor input being shut off by the control transistor so as to prevent erroneous operation of the motor just after the power supply switch is turned on or to prevent the production of a chattering sound caused by the operation of gear trains with the motor.

Abstract: This invention relates to a control circuit for a motor for use in driving an electrically controlled door such as an air mixing door, inner and outer surrounding air ventilation door, and mode change-over door etc. or an electro-magnetic solenoid for operating an injection pump applied in a Diesel engine or another motor for use in opening or closing a window pane etc. and protects the transistors forming the control circuit.

Abstract: In an auxiliary apparatus for starting a diesel engine having a quick preheating circuit operable by the switching of a key-switch from its OFF to ON position and an afterglow circuit operated by the return of the key-switch from the ST position to ON position, there is provided a heat maintenance preheating circuit to maintain the temperature of the glow plugs for a predetermined time after the quick preheating operation is finished. The heat maintenance preheating circuit for maintaining the temperature begins its operation just after the immediate heating operation by the quick preheating circuit is finished, and continues its operation for a predetermined period while the key-switch is at its ON position. As a result, even when the engine is not started to operate immediately after the initial preheating, the temperature of the glow plugs is kept at the predetermined temperature, thus assuring smooth starting of the engine.