The circuit shows a 135 -bit circuit . The circuit is mainly composed by the counter C180 and TWH8751 . The components along with TWH8751 frames an oscillator , and its frequency is about 1kHz. Count switch circuit K2 by the location of the holes in the 135 film fixed with epoxy resin piece brass contacts emerged from a wire and the body composition, when the volume chip 135 moves, each skip a small square hole , then touch Film contacts with the body once , producing a count signal . Boot , because the first hole of the contact plate and the body has been in contact , C180 has been reset . When a photo of the first nine holes produced eight count when the arrival of the signal , then the Q4 C180 showed high , so that BG conduction , the oscillator TWH8751 for “ST” input LOW and Starts to oscillate , the output signal from the pin driver the speaker sound , this master photo in place .
For Circuit debugging, first close the count switch K2, and then close the power switch K1, so that LED lights , Q1 ~ Q4 are low . K2 together again and then open a total of eight times on , Q4 is high , by adjust ing R2 so that BG turn ON and we hear the speaker voice , by adjusting R4, we can change the pronunciation of tone , by adjusting R5, we can change the intensity of the volume .