Doorbell Integrated Circuits - HK522

 Dual tone sound effect , " Ding - Dong ",
    " Ding - Ding " and " West minister bell "
    for 3 sounds available .
 3 alone sound output from 3 alone trigger
   pins touched .   
 Trigger mode by one shot re-trigger type .
 SQ pin available, 3 sounds can be
   sequence output when SQ pin is sequence
   triggered .
 Sound quality can be modify from Rosc (
   oscillator resistor ) value .