A traditional Telco has thousands of terminals with 50VDC on them, that you will work upon without fear or caution or even noticeable tingle.
Only a few milliamps of current are available there.
However, occasionally a pair of those terminals will provide around 130VAC (also current limited) which will startle you if digging around in the jumpers at that moment, or maybe you have your forearm resting on the block.
The 50V is what "powers" a landline phone's voice circuit and dialing at your house, the 130V rings the bell.
Above, the underside of the block goes to the switching line cards the jumpers on top of the block go to another block exposing the cable pairs that go to your home or office. Those are usually mounted vertically on the backside of the above thing, called the Main Distribution Frame.
Only a few milliamps of current are available there.
However, occasionally a pair of those terminals will provide around 130VAC (also current limited) which will startle you if digging around in the jumpers at that moment, or maybe you have your forearm resting on the block.
The 50V is what "powers" a landline phone's voice circuit and dialing at your house, the 130V rings the bell.
Above, the underside of the block goes to the switching line cards the jumpers on top of the block go to another block exposing the cable pairs that go to your home or office. Those are usually mounted vertically on the backside of the above thing, called the Main Distribution Frame.
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