Singlish | 
20 dollar circuit problem
During lecture yesterday Prof Liew gave us this fun question.
You have a 50Hz AC power supply, lamps LA and LB, push buttons A and B. When button A is pressed, lamp LA lights up. When it is released, LA goes off. When button B is pressed, lamp LB lights up. When it is released, LB goes off. When both A and B are pressed, both LA and LB lights up. When A and B are released, both LA and LB goes off. The circuit inside each box is unknown. Now find the unknown.
The solution is under $20, so you can forget about some high tech remote control electromagnetic thingie...
(the question was directed at the electrical engineering students, so don't feel bad if you can't solve it)
You have a 50Hz AC power supply, lamps LA and LB, push buttons A and B. When button A is pressed, lamp LA lights up. When it is released, LA goes off. When button B is pressed, lamp LB lights up. When it is released, LB goes off. When both A and B are pressed, both LA and LB lights up. When A and B are released, both LA and LB goes off. The circuit inside each box is unknown. Now find the unknown.The solution is under $20, so you can forget about some high tech remote control electromagnetic thingie...
(the question was directed at the electrical engineering students, so don't feel bad if you can't solve it)
Erm... I'm not sure if I understand the question right. If it is, isn't the solution very simple?