sundance-communications.com/forum Forums General General Telephone & Systems Information -48 Ground System

I am new to this forum but not new to this industry. I am a telco manager after 30 years of coming up through the ranks of digging ditches and climbing poles. I have a university education in electrical engineering and have been a COE installer and later engineer. So, I consider myself somewhat of an expert on basic telephony. But I got asked a question this week that stumped me. Why -48 power systems. (actually the question was why a positive ground) I started to lecture on electron donors and ions and corrosion and electrolysis but quickly painted myself into a corner. Anyone know the history of this?

I had always assumed it's primary reason was that a negative ground would remove material from the conductor through electrolysis, whereas a positive ground would if anything increase the size of the conductor through electrolysis. At least that's how it was explained to me many moons ago.

I was also told that it took a whole lot longer for the cable conductor to collect enough additional material for it to effect it's service life. I guess it was easier to shove more power down a line with a higher resistance/capacitance then it was to shove it down a line with a shrinking conductor. Smaller conductor's also had a shortened transmission range.

But, I may (and probably am) wrong on some of these things. If you stay tuned some real experts on the subject matter will eventually chime in. In this area I am unfortunately just an enthusiast at best.

I agree, but COE has a positive ground. You went down the same road I went. Seems like a negative ground would be better.

Sorry, got it backwards again. A conductor that is the electon donor collects the ions. So a negative ground system should plate metal out of the soil onto the ground rod. But the positive ground rod should be eroded away along with any cable shields exposed to the earth.

From Wikipedia:

The anode and cathode in the electroplating cell are connected to an external supply of direct current, a battery or, more commonly, a rectifier. The anode is connected to the positive terminal of the supply, and the cathode (article to be plated) is connected to the negative terminal. When the external power supply is switched on, the metal at the anode is oxidized from the zero valence state to form cations with a positive charge. These cations associate with the anions in the solution. The cations are reduced at the cathode to deposit in the metallic, zero valence state. For example, in an acid solution, copper is oxidized from an anode to Cu2+ by losing two electrons. The Cu2+ associates with the anion SO42- in the solution to form copper sulfate. At the cathode, the Cu2+ is reduced to metallic Cu by gaining two electrons. The result is the effective transfer of Cu from the anode source to a plate covering the cathode.

The cable shield is the anode in this picture.

Thanks. Better to lose some shield than pair. Phew. I knew I knew the direction of the ions... This must have coincided with the advent of underground and buried cables. I would not think OWL would care. But pulp in copper would.

Ya’ll… I sure think there’s some over thinking go on here.

In Direct Current, electrons from a more electrical source to ground over the path a least resistance in a one way stream. (holes flow the other way if you prescribe to that theory)

When measuring how much potential or force there is to push electrons from the current source we call that force, Voltage. (emf = electro motive force) Voltage is potential NOT flow.

The positive and the negative indications on a voltage measure meant ONLY signify the relationship of the points being measured at in relation the current source.

When measuring a phone loop we go tip to ring. Voltage being applied to the latter of the two. So when connecting a meter the relationship to the current source is negative.

Why apply voltage to the ring rather than the tip? … That goes back to manual operators and the old cord boards. …. The tip conductor has that name from the literal point on the connecter operators would use to stick in the subscribers hole… If the pointy end was the HOT (electrically charged from the current source) it would freaking arky sparky every time if the women didn’t hit the hole exactly.