We found this circuit in an old Mullard (Philips) documentation on the 555 and 556 integrated circuit (double 555). The relay must be 12 V with contacts that support the horn current.
This traditional doubler configuration with the 555 can be found in other articles on the author’s site....
This circuit, which appears elsewhere in this section but from other sources, was found in a book...
January 2017 - Mouser Electronics is announcing the availability of the new OptoMOS® CPC1010N...