| 摘要 |
An interface unit is provided for transmitting signals to and receiving signals from several transmitters. The improved interface unit includes a DC power supply, an active load, and a transmit/receive circuit connected to the fir t wire of a two wire circuit which transmits signals to and receives signals from the transmitters. The active load is connected in series with the DC power supply between the first and second wire of the two wire circuit and has a first impedance at DC and a second, higher impedance within a frequency range defined by the signals transmitted to and received from the transmitters.
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