| 摘要 |
PROBLEM TO BE SOLVED: To automatically set types of voltage supplied to a printed wiring board by providing a means of detecting the supply voltage of the printed wiring board and changing the types of supply voltage supplied to the printed wiring board according to the result of the detection. SOLUTION: An image expansion control section 201 is provided with a short jumper 103 as a voltage instruction signal generating means and is connected with a power supply through a relay 101 as a supply voltage change control means, using a voltage instruction signal line 102. The short jumper 103 is so constituted that it is opened when the supply voltage of the image expansion section 201 is 3.3 V, for example and is shorted, when the supply voltage is 5 V, for example. The power supply is so constituted that when the short jumper 103 is shorted, a current from the power supply excites the relay 101 and flows to ground through the power supply instruction signal line 102 and a power supply line 207 is switched to 5 V, and when the short jumper is open, the current from the power supply to the voltage instruction signal line 102 is interrupted and the power supply line 207 is switched to 3.3 V. As a result, the supply voltage is set automatically. |
