A latch circuit is supposed to lock on and off a load (such as a relay coil or a led light), through a momentary input signal.
Basically it works like a bistable relay, but backs to the reset condition when the power supply gets off.
In this article I'm going to talk about two latch circuits I designed and made for hobby purpose.
Both circuits use transistors. The first one latches a relay coil, whose contacts are also used to let the circuit work.
The second one uses just two transistors to latch a led light.