| 摘要 |
PROBLEM TO BE SOLVED: To discriminate between an AV plug and a headphone plug. SOLUTION: A four-terminal jack 60 has terminals 60a to 60d connected to respective terminals of an AV plug and a headphone plug. A movable terminal 60e contacts with a terminal 60f at plug uninserted time, and separates by insertion of the plugs. The terminals 60a to 60d are separated from output circuits 62 to 70 by opening of a switch 74. A signal generating circuit 78 impresses it on the terminal 60b by generating a plug discriminating probe signal. In the case of the headphone plug, electric potentials of the terminals 60b and 60c become equal to each other, and in the case of the AV plug, they become inconsistent. A comparing circuit 84 impresses a comparing result on a control circuit 86 by comparing the electric potentials of both terminals 60b and 60c. The control circuit 86 connects the terminal 60a to 60d to a switch 72 by stopping an impression of the probe signal, and connects the terminals 60a to 60d to the proper output circuits 62 to 70 by switching switches 72a to 72c according to the comparing result of the comparing circuit 84 by closing a switch 76. |
