This circuit is from an American 80's documentation. The circuit indicates when the voltage of a 9 V battery drops below 7 V. The transistors can be BC548.
This circuit, from an old ON Semiconductor publication, suggests a shield to excite an LED from an...
This circuit was obtained from an old American documentation having a limited adjustment range....
Microchip Continues Expansion of AVR Microcontroller Product Line with Addition of Three New...