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 previous oscillators that use gatesshown in this section, and the 4093 in the basic version,...
This voltage controlled oscillator uses a varicap to change the frequency. Usin a 100 turns coil...
The circuit shown in the figure is indicated for alternative sources of energy, such as those...