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Query

pvmb
Aspiring Pro
Posts: 490
Thanks: 47
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Registered: ‎12-02-2014

Query

In the context of a landline phone line, does anyone here know what "Earth A" means?
TIA
5 REPLIES 5
2u2me
Pro
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Registered: ‎27-09-2013

Re: Query

If you think of the telephone circuit coming from the exchange the positive (+) is called the B leg and the negative (-)  is the A leg, so earth A means that the negative is in contact with earth somewhere on the line
HTH
pvmb
Aspiring Pro
Posts: 490
Thanks: 47
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Registered: ‎12-02-2014

Re: Query

Thanks, 2u2me. So that sounds like a fault to me.
2u2me
Pro
Posts: 350
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Registered: ‎27-09-2013

Re: Query

Yep its a fault, electric`s lazy, it will always take the shortest path, so you will not be getting the full 50 volts
198kHz
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Registered: ‎30-07-2008

Re: Query

For the record, under quiescent conditions the 'B' leg will normally be at -50V (negative leg), and the 'A' leg is earthed at the exchange (positive leg).
So, as 2u2me advises, 'Earth A' is a fault, and will be a greater or lesser problem depending on its location, and whether it's a full or resistive earth.
Murphy was an optimist
FTTC 40/10   Billion 8800NL
BT technician (Retired)
2u2me
Pro
Posts: 350
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Registered: ‎27-09-2013

Re: Query

As engineers we always spoke of EARTH A, BATTERY B.,exchanges work +ve earth so effectively the A leg is earth thus the B(battery) leg is -50v with respect to earth.Testing towards an exchange will show earth on the A leg.
sorry for any confusion.