A relay switch has a coil such that a predetermined voltage is imposed on one end thereof and the other end is grounded with a resistor therebetween, and when the voltage of the coil is at least a predetermined value, the relay switch is turned on and a power source is supplied to an electronic apparatus. A transistor causes the voltage of the coil to be at least the predetermined value by means of drawing in the current flowing through the coil and causing the current to flow to the ground without passing through the resistor when starting the supply of the power source, and after the start of supply of the power source, gradually decreases the amount drawn in of the current flowing through the coil, causing a decrease in a manner so that the voltage of the coil does not fall below the predetermined value.