is it possible to send two electrical signals in the same wire?

Answer 1

Yes, there are several ways of doing it.

1. time division multiplexing
2. frequency division multiplexing

These are the 2 main ways of doing it. There are many variations of those 2 methods, also.

3. Another way is if one signal is a DC voltage and the other signal is an AC voltage. You can send both on the same wire, by using a transformer at both ends, or DC blocking capacitors at both ends.

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Answer 2

It happens all the time in telephony (where it was invented).

You can have a DC signal and an AC signal, in the easiest example). Filters separate those two signals at their destinations.

You can combine a variable DC signal (4-20mA) on a sensor line with the analog encoded message that modern computers use to read it (Hart) to serve old and new on same wire pair.

You can have a high frequency carrier signal modulated with information and put several of those carriers on the same wire pair (analog modems).

You can have carriers that are carefully controlled in frequency each with their own data set (Frequency Division Multiple Access).

You can have messages that show up at different times under careful control and can fit thousands of signals on the pair (Time Division Multiple Access).

Answer 3

Not only can you send multiple signals through a single wire pair, but you can also send power.

Think about your TV cable. That is a single coaxial wire that has 200 channels of the worst humanity has to offer. So multiple signals does not always equate to a good thing... :-)

Answer 4

Yes, modulate the signals at two different frequencies.

Answer 5

Sure. It gets done all the time. It's called 'multiplexing'.

Doug