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I had recently asked a quiestion here: Will this circuit for quiz buzzers work? and I got this answer.

I am trying to understand the circuit and I have understood most of it but there is only one part that I am not able to understand.

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I don't understand electronics in theory properly so can you explain in simple english why this ground and resistor have been connected?

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I think that without that resistors, the tension of the base is not fixed and probably will float when the keys/buttons are open. – user41342 May 4 '14 at 21:52
@Luis What is the meaning of 'tension of base'? – Kartik May 5 '14 at 0:51
up vote 9 down vote accepted

Strictly speaking, they aren't required, but those resistors help speed up the turn-off of the associated transistors, and also help with noise immunity by pulling the base connections all the way to ground when the switches are open.

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The standard term for this configuration is "pull-down resistors". – keshlam May 5 '14 at 4:37

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