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 medium wave radio with germanium transistors is from a 1957 Raytheon publication. Modern...
This is 4-input audio mixer using an integrated circuit 741 and two more operational amplifiers....
This is the circuit of a sensitive analog multimeter from the 70s. Remember that in this type of...