In telecommunication equipment,why always negative voltage used?

Question

In telecommunication equipment,why always negative voltage used?

Answer 1

From an engineering perspective, the question should be, why are negative terminals of a battery grounded, when it should be the positive terminal?  The phone system has it correct, i.e. grounded the positive terminal.  This has to do with western ideas of positive being good and negative being bad.  Take a look at most batteries, especially button batteries where additional insulation would increase the battery size.  Which terminal is the case?  So back when the phone company didn't have plastics to make insulated containers, the positive was the container sitting on the ground.

Other phone company trivia:

Why "dial" a phone number?  The word "dial" comes from rotary phones where the dial came from clock/watch makers that had a ready made supply of disks that had 12 holes on them, which were called clock dials.

And where did on-hook and off-hook come from?  The switch-hook was made from hardware supply store hooks to hang the ear piece speaker.  Thus on-hook = circuit off, and off-hook = circuit on.

Where did Tip and Ring on a balanced circuit come from?  Take a look at a headphone plug.  There is the tip connection, then a ring and then a sleeve.  Also see original 310 phone plug, which is similar to the 1/4 inch phone plug. http://en.wikipedia.org/wiki/TRS_connect...

...ex-Bell Labs

Answer 2

You need to be more specific.

They use ICs like everybody else, and they all run on positive voltage.

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Answer 3

How are you obtaining the negative voltage? If you are using a voltmeter then your leads could be backwards.