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 page shows a crystal oscillator for 2 MHz. Other frequencies can be produced depending on the...
This circuit is from a 1970 publication. The time constant is given by 1.3R x C where R is the...
The supply voltage range of this circuit ranges from 4 to 20 V and the power depends on the chosen...