This circuit is from an old Mullard (Philips) manual with applications using the 555. Choosing appropriately the resistors and the timing capacitors, the ranges obtained can exceed days.
The frequency of this astable multivibrator depends not only on the capacitors, but also on the...
This interesting sound effect circuit that produces the sound of bulls or Bull Horn was found in...
This 1967 Raytheon circuit uses an optical coupler of the era and has a range of 800 to 200 Hz....