How to make an bistable multivibrator with descreet components
A bistable multivibrator has two stable levels. When you press the left momentary (door bell-type) switch you will cutoff the right transistor (you grounded the base while you pressed the switch). Base current will now go to the left transistor through the right LED and resistor. The left transistor reach a saturation state and short-circuits the switch, exactly as if you pressed the switch the whole time. The right transistor can not get any base current until the right switch is held down. Then the whole discussion is reversed.
Again the LEDs and resistors can be replaced by relays to control other circuits. With the two LEDs you might use it as a "first come - first served" device
TUN = Transistor Universal NPN, BC 107, BC 547, 2N2222, etc.
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