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reed switch(occupancy light) this circuit is a occupancy light circuit i want to know the working of the transistor regarding base,collector and emitter in the transitor

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    \$\begingroup\$ Your question is very broad. Can you edit your question to explain what you do know and where you are stuck? \$\endgroup\$ – Transistor Nov 12 '17 at 13:59
  • \$\begingroup\$ Try simulating it, it's actually quite a fun little circuit to play with :) As a clue, think where the current will flow when the switch is open and closed. Let us know your working, and thoughts (nothing original yet) and you'll get more help! \$\endgroup\$ – awjlogan Nov 12 '17 at 13:59
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You really should use component designators in your schematics. Lack of them makes it more difficult to talk about the circuit, so I'll be more brief.

Consider what happens when the reed switch is open. The first transistor is on, lighting the first LED. The collector being low also turns off the second transistor, which keeps the second LED off.

When the reed switch is closed, the first transistor is forced off, so the first LED will be off too. The second transistor is then turned on, which lights the second LED.

In summary, one LED is always lit. The reed switch state governs which one.

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  • \$\begingroup\$ can u explain in detail on whats happening in both the transistors \$\endgroup\$ – Santosh Divakaran Nov 12 '17 at 17:13
  • \$\begingroup\$ Whoever downvoted this, what exactly do you think is wrong? \$\endgroup\$ – Olin Lathrop Nov 12 '17 at 22:08

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