A circuit based around the 4081B integrated circuit can be seen below. The integrated circuit (IC) contains a number of AND gates, although for this sample circuit only one of the AND gates has been used.

The circuit above represents an AND GATE. This means that switch one AND switch two must be pressed before the relay is energised. When logic chips are used in a circuit the inputs of any unused gates should be connected to the positive or negative, it does not matter which.
The ‘chip’ diagram opposite shows the gates of the 4081B and its inputs and outputs. In the circuit above only input pins 1 and 2 are used, for the switches, which when pressed produce an output at pin 3. The output at pin 3 energises the relay and starts the motor, releasing the food for the dog.

QUESTIONS:

1. How many switches can be connected to the 4081B ?
2. Draw a 4081B circuit diagram with three switches connected.

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