JPS57196318A - Level converting circuit - Google Patents

Abstract

PURPOSE:To detect accurately a water power level corresponding to a switching mode and to realize the level discrimination, by using a variable impedance connected to a switching element and a means having a level discrminating function. CONSTITUTION:For instance, resistances 24 and 25 of a variable impedance circuit 8 are set at 10KOMEGA and 3KOMEGA respectively. The common contact 21 of a changeover switch 20 in the circuit 8 has the conduction to an individual contact 23. Under such conditions, the common contact 4 of a switching element 3 has the conductiln to an individual contact 11. As a result, the voltage V19 at a joint 19 is higher than the discrminating level Vl of the circuit 8, and accordingly, the contact 21 has the conduction to a contact 22. Thus the voltage of the joint 19 increases, and a microcomputer 2 discriminates the voltage at an input terminal 7 as the logical value 1. When the contact 4 of the element 3 has the conduction to an individual contact 10, the voltage 19 is set at a level obtained by dividing the voltage of a power supply 18 which is equivalent to the voltage drop of a car body. The voltage V19 is lower than the level Vl, and the contact 21 has the conduction to the contact 23. As a result, the voltage V19 is reduced. The computer 2 discriminates this voltage as the logical value 0.