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88 I-CONNECT007 MAGAZINE I MARCH 2026 polarity of the current flowing in the transmission line from the source to the load. In reality, the net we call ground (GND) is, actu- ally, just the reference net that all other nets are referenced with respect to. To emphasize the true nature of this net, we should use the term "Return" (RTN) instead of GND in our circuit designs. I believe the use of "ground" in early electron- ics circuits comes from the telegraph days, when telegraph wire was run on the poles between the different telegraph stations. The "ground" was then wired to a copper or other conductive rod sunk into the actual ground about 4 to 6 feet. This created a transmission line loop between the signal wire on the pole and the earth be- neath it (Figure 1). In Figure 1, the circuit has a 10 kV DC source powering a 100k ohm load. Note that resistor R1003, the 1-ohm resistor on the middle rail, is added to the simulation to allow SPICE simu- lations of both ends of the wire. This is a 100 mA current in the lower loop. In the top loop in Figure 1, an LED circuit is powered by a 5V DC source whose negative terminal is connected to the positive terminal of the 10kV DC source. In Figure 2, the peach-colored signal labeled as V(V5) measures 10.005kV with respect to the GND terminal. Since the net labeled as V_10K_ RTN is at 10kV, this indicates that the total voltage seen across LED and Resistor of the top loop is only 5V, meaning that the current through the LED is only 10 mA approximately. This shows that any Figure 1: An example of a transmission line loop between the signal wire, the pole, and the earth beneath it. Figure 2: The peach-colored signal labeled as V(V5) measures 10.005kV with respect to the GND terminal. which indicates that the total voltage across the LED and the resistor in the top loop is only 5V, and the current through the LED is only 10 mA.