| 摘要 |
PURPOSE:To prevent a system from being electrically broken due to the erroneous insertion of a unit by comparing a specific signal outputted from a connected unit with a specific signal of a unit to be substantially connected, and only when both specific signals coincide with each other, electrically connecting the unit to the body side. CONSTITUTION:When a power supply is turned on after surely inserting units into a connector 2 on a back board 1, specific signals are sent from respective units through signal lines 201 to 203 and compared with a signal equivalent to the specific signal of a unit to be substantially connected to the connector 2 by a comparator 4. When both signals coincide with each other as the result of comparison, the output 401 of the comparator 4 is turned to a high level, respective 3-state buffers 3 are enabled and the units are electrically connected to the body. When both signals are different from each other as the result of comparison, the output 401 of the comparator 4 is turned to a low level and respective buffers 3 are not turned to the enable state and held at an electri cally disconnected state. Consequently, the system can be prevented from being electrically broken due to the erroneous insertion of respective circuits on the unit side and the body side. |
