Circuit diagram


















    
    
   

2 0 V










 






 

3 V 3
R78
10k


3 V 3

R77
10K



3 V 3

R76
10k


3 V 3


10k


3 V 3

R74
10k



3 V 3
R73

10k




 





sw






sw





 

 









 








 20  
  