If I have more than one sensor that provides a digital output (1 or 0 only,) and I only have one pair of wires connected from all the sensors to a specific point (assume the sensors are at point A and I would like to transfer the data to point B using one pair only) what are the possible ways to do that using only one pair of wires?
I also would like to mention that from point B I assume I can know which sensor is sending 1 and which sensor is sending 0.
This can be achieved using time division multiplexing where signals are sent at fractions of a common time period. This is achieved using synchronized or asynchronized switches.
Refer: https://en.wikipedia.org/wiki/Time-division_multiplexing
MAX9205 serializer and MAX9206 deserializer: -
10 digital input lines on the left and 10 digital output lines on the right. One pair of wires in between. If you use the MAX9207 and MAX9208, the payload data rate (on the single wire pair) can be as high as 660 Mbits per second.
You don't explain your sensors, how they are powered, the distance involved or lots of other aspects that are important.
However, if your sensors are a simple on/off signal (relay or transistor/FET to ground) then you can simply make a current loop sensed by an MCU A/D. Show below is two relay points as an example, you could scale the currents to suit an application:
UPDATE: Since the OP now asks about 4 sensors, I updated the schematic to show 4 inputs.
simulate this circuit – Schematic created using CircuitLab
Since most A/D will run between 15kHz and 100kHz you can sense which sensor point is on or off (or both of them on/off) with reasonable timing accuracy. This would scale to 6-8 sensor points if required.
If the sensors need to be powered across the single pair of wires it becomes a little more complex but still quite simple.
