| 摘要 |
PURPOSE:To save the consumption of the power of a power source by connecting power to an external electric circuit only when current by the change of the density of a magnetic flux passing through an induction coil is larger than a threshold, and cutting it from an internal electric circuit after measurement for a prescribed time. CONSTITUTION:A current comparator 5 cuts small current due to the disturbance of magnetic flux by the various influence of magnetic fields occurring in the periphery of the induction coil 1. Only when prescribed threshold current is generated, a power connection signal A is made active. A switching means 3 usually opens a path (a)-(c), interrupts current from the power source 2 and prevents the consumption of the power source 2.When the signal A from the coil 1 becomes active, the path (a)-(c) is connected so that current is to be supplied to the external electric circuit. Then, current is supplied to the external electric circuit by a path B-(c)-(a) so as to operate it. The interruption means 4 of a counter circuit starts counting with the supply start of power to the external electric circuit, transmits an interruption signal D to a means 3 after a prescribed time passed and opens connection between the power source 2 and the external electric circuit. |
