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 is from an English magazine from 1976. By replacing the transistor for a BC548, the...
In the figure we have a configuration that allows to test NPN transistors and with the addition of a...
In the figure we have an IF amplifier step using a MOSFET. The circuit was found in a 1980s...