This circuit should only be used with the solenoid type chime doorbells, the electronic type that play tunes will not work here.
The hardest part for this circuit was the title. It is quite easy to miss the sound of a doorbell if you are watching TV , this circuit gets round the problem by providing a visual indication, i.e. a lamp. As an alternative, a LED could also be used. You could just parallel a lamp across the doorbell, but this would mean extra drain from
the doorbell batteries or transformer. Using a series resistor R1 actually reduces current flow , and if run from batteries, will give them a longer life. The value of R1 is chosen so that about 0.6 to 0.7 volts is dropped across it, and the doorbell should
still ring. I used a combination of a 22 ohm resistor in parallel with a 50 ohm. The doorbell still rang and circuit operated correctly. I used to have an electromechanical counter that registered each time when someone pressed the switch....in fact, I remember a time when I had more "hits" at my doorbell then at my web site=:)