What are the two devices in the power system
Connect the two device circuit, called the two line. In the two line of DC is generally used for communication detection equipment, such as PABX, PDH, MUX, generally for 48V DC power supply, AC line for AC equipment use
. Such as measuring instruments, relays, switches, buttons, automatic control equipment, computers, signal equipment, control cables and some power supply devices, etc..
Your question is somewhat ambiguous, as I understand the following: the two equipment is a device for the work of the control, protection, monitoring and measurement equipment
