I was taking apart an old game-show buzzer system (like something they might use on Jeopardy) and I was confused by the a particular section of the circuit board:
I'm pretty sure the circular component labeled "W005G 840A" (datasheet) is a bridge rectifier. It is connected immediately after the power coming from the switch.
This board runs of a 9V DC wall supply, so why would they add a rectifier? It seems to me that all it would do to a DC voltage is drop it slightly.
I thought it might be used for some sort of circuit-protection, but I don't understand what they are protecting against. Wouldn't the 9V wall adapter prevent any harmful voltages from reaching the board? Also, if they are trying to protect against reverse polarity wouldn't single diode work fine?