Found in a 1980s American documentation, this circuit appears with variations elsewhere in this section. The circuit activates a relay according to the supply voltage.
This preamplifier circuit for turntable cartridges was found in the March 1994 issue of...
This circuit was found in a Hands On Electronics from the 80's. The circuit emits an audible alert...
This high impedance input amplifier is suitable for the use with piezoelectric sources such as...