This approach alarm circuit was found in the September 1970 Radio Electronics issue. The 1 mH coil is wound on a ferrite rod. The relay is 12 V sensitive.
This circuit was found in a Signetics documentation from the 1980s. The integrated is a PLL and...
This two-channel wired intercom was found in the April 1990 issue of Radio Electronics magazine....
The output voltage of the circuit shown in the figure is approximately 7.0 V for a 15 V supply...