| 摘要 |
PURPOSE:To decrese the number of operation keys on a front panel and to reduce the cost of each audio device, by controlling an electronic machinery such as an audio amplifier, a tape deck, etc. with a set of a switch groups. CONSTITUTION:First an amplifiying circuit (a) is selected by a circuit selecting switch 2, and then a circuit changeover switch 10 is closed with a circuit changeover switch 11 opened. In this case, a holding through gate H1 is in a holding mode. Then an optional switch Sn is closed in a switch group 1. Thus the output of an NAND circuit 3 is set at a high level, and a pulse is produced from a pulse generator 4. If this pulse is supplied when the switch 10 is closed, the gate H1 is changed to a through mode from the holding mode. Then a digital data produced in response to the switch Sn is fed to the gate H1 to be supplied to a variable impadance circuit 8 in the form of a control signal. Thus the circuit 8 varies the impedance of transmission in accordance with the control signal. Then the control of volume is carried out. |
