/diy/ - Do It Yourself

>>1515299
Pic related shows more illustrative symbols for the jacks with switches
when unplugged (left), the switch contacts touch the jack contacts. when plugged (right), the jack contacts are pushed away from the switch contacts and therefore disconnected. usually this is used to pass an internal audio signal to the switch contacts, to be interrupted when an external signal is plugged in
if there is a resistor pulling down the jack contact and a larger resistor pulling up the respective switch contact, the switch contact voltage will be low when unplugged, and high when plugged
does it make sense now?

>>1515301
not much to it. add a resistor to limit current. on the web there are LED resistor wizards to get you started, given the LED voltage drop (should be specified), the supply voltage, and the number of LEDs, they will give you a resistor value and power rating required