how to determine opto switch pins

i've bought a opto switch and, what's written on it is this:
"
kt 3162
8731
mexico
"
i've searched alot on the internet to find a datasheet but didn't find any.
any body knows a way to determine which pins are for the diode and which for the phototransistor?
tnx in advance.

Are there any markings either on the top or near the leads? Letters such as E and S for example.

Keith

I guess, it might be a MOC3161 (optotriac with zero crossing control) equivalent.

But if it's a phototransistor though, most have an industry standard pinout, you can refer to similar types. The LED can be easily identified with a multimeter (in diode voltage range), also the base pin of the optocoupler if connected to a pin.

there's no marking on it
i just tried with diffrent orientations and found the right one
tnx for your replys

In case of doubt, the text orientation defines the pin 1 position (lower left corner).

yes , when i put the device in the right orientation which the text is read,the emmiter pin was the lower left corner
in all the datasheets a i saw for other models the emmiter pin is no. 1
tnx