Using a step up/down transformer, what is the input? the wall or the source?

Question

Using a step up/down transformer, what is the input? the wall or the source?

Answer 1

The input is the source usually. However, a step up/down transformer can be connected in reverse.

If you have a 120 to 240 volt transformer, and 120 volts mains,  then you can use it to step up 120 volts to 240 volts. In that case, the input is the 120 volt winding and that is connected to the wall, ie, the mains supply.

If you have 240 volts mains, then the same transformer can be used as a step down from 240 to 120 volts. In that case the input is the 240 volt winding and that is connected to the wall, ie, the mains supply.

Answer 2

input is the power source where you live,USA is 115 volts AC.

check the transformer where it marks 115 v or 110 v or 120 v,it has two wires,connect this two wires into a power plug then plug it into the wall power outlet.

For other country in the world, input can be 240 v or 220 v or 200 v.

Transformer can be worked on 50 cycles or 60 cycles or 400 cycles.