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What is function of the resistor??

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ilikebbs

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Hi, anybody can tell me what is the function of the resistor.

As I know that usually a diode is used for the inversed DC input.
 

I think pin 3 is for detecting if any jack is inserted. When it does, the arrow would not touch the negative terminal.

So, in a case like this, the R is just to avoid short circuit if... the positive and the negative terminal touch the inner contact of the socket but the jack hasn't plug in completely.
 

its very simple man ......
resistor is to draw the current 4m the voltage source when 3 is detecting any device thus grounding the arrow..
it is because if u connect any voltage souce directly to ground then there will be short ckt !!!!!!!!
 

Actually, I didn't understand all thoughts that have been expressed previously, but no problem.

A similar resistor for sure isn't generally used with DC input connctors. I have designed a lot of devices, that never needed it. So it must have a particular purpose. Not knowing the remaining circuit or the application, I can only guess.

It could be, that the circuit has a design flaw and get's damaged when connected to a switched-off power supply but the device has it's internal decoupling capacitors yet charged. The resistor could prevent this by discharging internal capacitors. Also other device properties may require a complete discharge of input voltage.
 

Also if device has a sleep mode device is acting as load for incominng power supply to keep it warm
 

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