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.
April 2017 - Microchip's new 4-port KSZ8864 switches for VoIP, Games, Automotive Ethernet,...
This circuit adds a beep to turn on with car flashers that do not have this feature. A 47 ohm to...
Figure bellow shows how the 4510, a divide-by-1U, up/down counter with three-state outputs is...