It is basically a sensor and data receiver / display connected together by the minimium of wires...
The power requirements for the sensor will be supplied through the same wires that the sensor sends the signal.
This could be an aerial masthead amplifier using the dc sent up the coax to power it to send the signal downwards...
It more likely is for a sensor to be powered from its 4 to 20 mA loop connection with its receiver and at the same time sendine the information over the same line... A sort of loop!
John.
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