This circuit was found in the July 1986 issue of Radio Electronics magazine. The circuit has a loudspeaker warning system. The sensor is the ceramic capacitor C1 which acts as a transmission line.
This circuit was taken from old American documentation. The transistors used make it possible to...
This oscillator uses a general-purpose transistor that can have BC548, BF494 or 2N2222 equivalents and...
This circuit of a 73 American magazine from the 1990s can generate multiple frequency signals from the...