One shot TTL
Électronique / Electronic
7400

Does the term "one-shot" mean anything to you? (No, it's not a nickname for some cowboy ... or a gun that holds just one bullet!)

If you're stumped, take a look back at Project A "one shot" multivibrator.

When you finish the wiring connections, Put ON the power. Press the Key once and watch what happens to LED 1.

Try holding the Key down for different periods of time ... does LED 1 stay on the same length of time or does it vary?

You see that a one-shot multivibrator will have an output for a certain length of time regardless of the length of the input (it "fires one shot"!).

This means that it can be used in many circuits as a timer. You might also see this circuit called a monoslable multivibrator. Since this is a multivibrator, you might suspect that there's some way to vary the time it produces an output.

You're right - there is a way — and we'll let you try to discover what it is. (Actually, you shouldn't have much trouble discovering which parts you need to change. Be sure to make notes about the effect of higher and lower values on circuit operation.)