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 transmitter for the 7 MHz range, as we can assume by the number of turns of the coil, since the...
This circuit was obtained from a 1967 General Electric documentation. The circuit makes use of...
This circuit is from an Electronic Design of the 90's. The circuit can be implemented with more...