| 摘要 |
PURPOSE:To confirm whether a key input has been received or not by constituting the titled device so that when a key monitor signal is inputted, an arithmetic control circuit counts a timing signal and monitors a pattern of a service tone, outputs a pattern of a sound corresponding to a key monitor sound to a changeover switch, and generates a key monitor sound. CONSTITUTION:Various service tones and key monitor sounds re generated by an oscillating circuit 1 for sound source, amplified by an amplifier 3 through a changeover switch 2, and generated from a loudspeaker 4. The changeover switch 2 is controlled by a signal from an arithmetic control circuit 5. A key input signal is latched and decided definitely by a timing signal of 16Hz which has been inputted to the arithmetic control circuit 5. In this way, when various service tones have been generated from the loudspeakers through the amplifier circuit 3 by controlling the changeover switch 2, even if a key is inputted, whether the key input has been received or not can be confirmed by generating the key monitor sound without varying greatly a pattern of various service tones.
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