| 摘要 |
An electronic bell sound generating circuit for a timepiece for generating a sound simulating a bell sound produced by a motor driven bell-striking system. The circuit includes an audio frequency signal generating circuit, an optional number of attenuation-modulation circuits, an alarm trigger circuit, an attenuation control circuit and a sound generating circuit. The audio frequency generating circuit includes a reference signal generator and a frequency dividing circuit. The attenuation-modulation circuit includes MOS transistors connected in parallel and gate circuits connected to gates of the MOS transistors. The attenuation control circuit includes shift registers comprising flip-flops connected in series. The circuit works to stepwisely increase the combined on-operation resistance of the MOS transistors to thereby decrease the value of the current of audio frequency signals to the sound generating circuit in order to obtain an attenuated sound. When two or more attenuation-modulation circuits are provided, different audio frequencies are supplied to each respectively and the output signals from the respective attenuation-modulation circuits are superposed in the sound generating circuit. The time cycle for stepwise decrease of the current value of the audio frequency signals is set at 0.0625 seconds.
|
