Digital-analog converter circuit for speech-synthesizing electronic timepiece

An electronic timepiece powered by a battery and having timekeeping circuit means for producing signals indicative of time information, memory means storing data relating to acoustic signal synthesis in digital form, control circuit means coupled to receive said time information indicating signals and responsive thereto for reading out portions of said data stored in said memory means, digital acoustic synthesis circuit means responsive to signals from said control circuit means and said data read from said memory means for generating a succession of digital signals each specifying at least one amplitude during a predetermined time interval of a portion of an acoustic time indication signal required to be audibly reproduced to indicate said time information, and digital-to-analog conversion means, comprising:

• pulse width modulation circuit means responsive to successive ones of said digital signals for generating a train of pulses wherein the duration of each pulse is proportional to a numeric value represented by a corresponding one of said digital signals from said digital acoustic signal synthesis means;
• pulse amplifier means coupled to receive said pulse train from said pulse width modulation circuit means;
• and
• electro-acoustic transducer means coupled to receive said pulse train from said pulse amplifier means, and responsive thereto for eliminating frequency components of said pulse train which are outside a frequency band containing said acoustic time indication signal and for reproducing said acoustic time indication signal in audible form.