2 or 4 or 8 channel analog multiplexer

[chupa 0]

Is there such a device to send 2 or more 4-20mA signals over a single pair cable, digitally or however it needs to a box on the other end that will split it back up to its analog form? The protocol it uses to send over the cable is irrelevant as long as the signals on the other end are intact and update at least once per second. Is there a wireless version of the same thing that will work over 300’ open air?

[JRoss 84]

You should look into fieldbuses (Modbus, DeviceNet, Profinet, etc.) for the wired solution. For the wireless solution there are a number of products on the market, and some of them use the same fieldbus protocols. Best choice depends on the application, location, and hardware (sensors, PLC, etc.) being used.