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.
The circuit presented generates short pulses. This configuration was found in a publication from...
This circuit is from an English publication from 1993 but can be easily assembled with the BD135...
What this circuit does is change the logic level of a signal thus serving as a different logic...