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 circuit appears elsewhere on this site using the most diverse transistors. This version is...
Frequency in this oscillator is controlled by a crystal. Any 1 MHz to 15 MHz can be used. The JFET can...
This was one of the National Semiconductor clock modules very popular in the 70s and 80s. In the...