| 摘要 |
PURPOSE:To keep musical scale to a prescribed frequency while a key is depressed, by storing a musical scale setting ROM output to a latch during the depression of the key and switchingly controlling an oscillating frequency of an oscillation circuit through the detection of this latched output. CONSTITUTION:In an electronic desk top calculator with melody, a phenomenon that a musical scale is changed through the change from a high frequency during operation into a low frequency of post processings on the way if a key is kept depressed, is prevented. When the key is depressed, an output IC1 of ROM for musical scale setting is outputted and a tone scale frequency corresponding to entry keys is set. This output IC1 is stored in a latch circuit I1. The output of the I1 is detected at a detection circuit 9 and an oscillation circuit 3 is oscillated in a high frequency. While the tone is given, an output of a NOR circuit NR4 of the circuit 9 goes to ''0'', and even if an operation display switching signal goes to ''1'', the output of an AND circuit AG remains ''0'' and the oscillation frequency of the oscillator 3 remains to the high frequency, then the musical scale can be kept to a prescribed frequency during the depression of the key. |
