If you had posted a schematic of the circuit the button is connected to Crossroads could have determined if a transistor would work but since you gave no such information you left him with no other options. If you are asking for infomation on how to modify "another circuit" it help if provide something more specific than "another circuit". He didn't ask you what "another circuit" means because generally when posters are that obviously vague about their circuit it's because they don"t want to discuss it ( ie: marajuana grow farm ,I.E.D. etc. etc ).
We get posts like " How to I send a trigger signal 3 km wirelessly ? That's a direct quote.
Sorry raschemmel, it was more that I still don´t know how to express what I need than being vague, I´m going to try to put it like an exercise for myself so I can begin to have things clear, my field is Software, so I have so much to learn..
Imagine we have this both circuits, they are the same one repeated, each one with it´s own battery, i need that they will be able of:
1 . Use button 1 of circuit 1 regular, so the led turns on
2 . Use button 2 of circuit 2 so it does its dutys, and it also turns on the led of circuit one.
3 . It need to drive a safe signal, so, when both interrupts are on, I don´t fried the led of circuit one,
Transistor can maybe work, but if you want keep the two circuit isolate you have to use a photocoupler, with the transistor you have to share at least the ground.
It´s important to maintain the design as cheap as possible, it´s very important to protect both circuits, but i think it´s doable with transistors, so it would be my first choice.
The original circuit i guess it will be more complicated, since, I have a High signal when the button of the slave circuit is not pressed and Low signal when it´s pressed, but for the moment, it´s enough for me so I can figured it out what´s going on.
Thanks again for the answers!