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.
We found this circuit in a European publication of the 1980s. The transistor could be the BC549. The...
Found in a 1963 documentation, this circuit employs germanium transistors of the time. Transformer and...
This circuit takes advantage of the temperature variation of the component with the air flow that...