I Am not sure which diagram you are looking at but when I connect a opto to
A transistor, the base of the output transistor (I.e. 2n2222)connects to the Emitter or collector (depending how you wish the output transistor to work ) Of the opto transistor.Over here I set them up all the time to switch TX on Different radios and we use a 4n28 with a bc548 or bc558 as a output Sometimes they drive a relay off the BC with no problems.In most optos the Anode and cathode (input side)of the opto are connections to the led that Provides the light inside the opto to drive/switch the small current Transistor on the other side of the opto(Output side) On a transistor the base is the low current input that switches the the Collector and emitter which are connected to the higher current loads Thank You, Ian Wells, Kerinvale Comaudio, 361 Camboon Road.Biloela.4715 www.kerinvalecomaudio.com.au
