5V supply to refit into a vintage "ding-dong" wired chime doorbell; the classic type with a centre striker that strikes the chimes when the solenoid is energised through the doorbell button.
When the button is pressed, current is pulled through the double pole relay, closing the contact and latching it on. Remaining charge dumps through the doorbell chime solenoid to strike the ding chime.
When the charge current slows, the relay opens again and the solenoid field stops. The striker is pushed by it's compressed spring into the dong chime.
The doorbell can't be mashed rapidly until the capacitor has enough charge to switch the relay again.
