Actually the relay is connected to the LED bulb. i.e. when ever a signal comes from the other end, the relay will on the LED.
The term "indication" we use with the relay, is actually used to categorize the purpose of the relay in the system. Nothing more:).
So how many relays do you want to control, that is turn on an off.
say about 100 that we need to control(on/off)
and 100 which we need to get the status whether its on/off.
What makes them go on or off. If it is command from a computer what form does that take? Is there a program on the computer that is running or do you have to write one?
They need to be turned on when we click a button on the computer. We have to write a program for that .