i have manage to come out with the circuit from a door bell.

i would like to know what is the IC chip that is being used ....
and also what type of transistor is used? (NPN/PNP)?
what is the rectangular thing with a hole (black colour)?

 

The IC is the famous 'Melted Blob' IC. No idea.

 

what is the rectangular thing with a hole (black colour)?

Voltage regulator I would say

 

Hi Kux,
I dont know if this info will help but might give you some leads.... the Black blob, is called (Chip on board (cob) for short.. its just a chip in there that does the bell ring, as for the Transsistors.. they are I reckon to amplify the sound otherwise it would be to weak to hear..

Go to www.rapidonline.com then go to semiconductors, then Timers & sig Generators then choose the Ding dong chip!! it also gives a pdf File on how to wire it up..

Yes Ive wondered about these black blobs.. so I found out some of them hope this helps
redlight

 

I have one of those blobs in my bathroom scales. Are you sure this is a door bell?

 

I don't think it's an IC. I seen one once that had tiny resistors and such underneath. I think it's more of a way to protect the tiny components from the outside elements or what ever.

 

It's a substrate mounted directly on a board, then a blob of black epoxy is placed over it.

That saves on production costs, and certainly makes it harder to reverse-engineer.

This thread is not going to go anywhere.