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, obtained from old documentation, allows the recovery of sulfated batteries. The...
This 80's circuit uses a small light bulb as an indicator, but an LED with the appropriate resistor...
This amplifier with the RCA CA3018 integrated circuit was found in the August 1970 issue of Radio...