What does this do?

[GatorGnet]

What does the 4k7 resistor do in this schematic(red arrow)? If the pin is set to high, wouldn't this resistor create a short?


**broken link removed**

 

[mvs sarma]

while the transistor is ON it would help as bottom part of the potentiometer , the upper one being the series resistor on base.
while in off condition , it would provide a termination for the base, as otherwise the base would be floating with a long wire and possible induction there of,

 

[pcbheaven.com]

pull down resistor

 

[crutschow]

It shunts away any transistor base leakage current when the transistor is off.

When the transistor is on there will be a current through it of about 0.7V ÷ 4.7k = 149µA (for a silicon transistor). The rest of the current through the RB1 input resistor R will go into the transistor base.