Dont know why this came to mind, guess its my 40 year old memeories catching up with my 71 year old brain. Back in the day when I could barely spell 1A2 i was working on a job somewhere and we were gonna run some circuits on a feed going to another building but pairs were short.The lead man surmised that we could just make it if we eliminated the LGs and A1s and picked up the ground in the other building.His theory was the old adage " Grounds ground the world around". I dont remember if it worked.Anyone know if it would. This was back in the early interconnect days where we only had to get it to work once.
That was an old saying, but ground is not ground the world around and that's why bonding became so important. Back in the old days of magneto phones there was a hot and the ground was picked up at the end point. While it worked it was often noisy because the ground was not pure or filtered.
The potential to Ground at various places - even within the same building is not always the same. There could be several volts difference.
Depending on the circuit it might not matter - or might matter greatly.
Sam
I have used that method with success many times. There are, in fact, tie lines, private lines, and signal circuits that are designed to do just that...rely upon a ground connection at each end...and they work perfectly using the only ground available at each end: the telco ground or electrical ground. As Sam said, there may be slight voltages present (usually in the millivolt range) but those are found when measuring the electrical ground to earth ground connections within a building. In the long run (so to speak) ground is ground the world around.
When the reference is -48volts or even 24 volts or possibly even 10 volts you're usually OK.
Arthur, you're not forgetting about the infamous "Remote Hold" are you?
I had a service call several years ago out on Long Island. Main Data Closet in one building on a campus and an IC in another building that probably wasn't 1,000' away. Users connected to equipment in the MC could sign on to any computer connected to the MC, but NOT to any computer or server in the IC. And vice versa.
The answer was the grounds. Each closet had their own ground bar and they were not common. Each of the closets were fed from a different electrical service. There was a 3 or 4 volt difference in potential between the 2 grounds. With a 5 volt power supply it was enough to cause headaches.
Sam
Guesss he could have sent one LG and one A1 and looped at far end.I shudder to think of some of the stuff we did in the early interconnect era.I recall when I started we didnt even crossconnect, just punched the station wire down on the switch side and that was on a 200 line hotel. Couple moves and beanies became valuable.Biggest part of the people hired at UCS in the early days were right off the street(like myself)
Sam, I thought we were friends...now you go and start swearing at me...
"remote hold" is a phrase that gentlemen do not employ when speaking to other gentlemen in polite society. It is a phrase that can cause a rash, or hyperventilation, or even violent mood swings in the persons familiar with that unsettling product offering, when present during the discussion.
When retired telephone men are interviewed and are asked what activities in their professional career may have caused their alcoholism, drug use or spousal battery, they invariably cite "trying to get the @#$%^& remote hold to work" as a "gateway" to their misfortunes.
Sorry, Arthur.
My feelings exactly. But so much of that circuit depended on the Distant Grounds being....at least close in reference to each other I felt it obligatory to bring it up.
I don't know if there are 6 people left on the Board who even know what it is, much less worked on it.
Sam
Well, I remember that there were the 1-pair method, the half-pair method, and the no-pair method, the last using the 400-type card that had about a pound of electronics on daughter boards, made by Melco (?). It relied, I think, on voltage drop for detection.
I remember a 6B, a 17B and an 18D relay all wired together and with a....½ pair between. I think a goat had to be sacrificed when all wiring was done to guarantee a successful circuit.
I'd heard of the Melco units but never used them.
Ahh, the days of Iron ships and wooden men - or was that the other way around? ;-)
Sam
Damn...I never considered the goat sacrifice method...I usually tried to find a sacrificial virgin, but in Harlem in the 1970's, one was usually sick and the other one didn't want to work by herself.
Sam
Arthur...I spit out my drink reading that one...lol