| 摘要 |
PURPOSE:To clearly show melody having sustain effect when playing rapid passage, by quickening the discharge time of a condenser corresponding to a key switch made before the make of some key switch when making the some key switch. CONSTITUTION:When making a switch SW1 by depressing a key at time t0, electric potential at a point C rises with a time constant R3 C1 up to +(Vcc-0.6)V. Meanwhile, approximate Vcc/R1 currents flow through an emitter of a trsnsistor Tr X1 by the make of the SW1, and the collector electric potential rises only by a voltage portion corresponding to R6 Vcc/R1 more than electric potential in case of the make of the SW1. The voltage is differentiated by means of a differentiation circuit C2X and R7 and changed into trigger pulses to trigger single, stable multivibrators X2, X3, the collector electric potential of the Tr X3 is conducted by means of a diode D3 as appoximate earth potential only by the time of a time constant C3, R8 from time t0, and electic potential at a point B is shunted to 0.8V only by the time. Thus, a condenser corresponding to the switch early made discharges. Consequently, melody having sustain effect can clearly be shown. |
