Why is the power supply of the solar container communication station negative 48V

Why do we use 48V power supply?

The choice of 48V was to maximize the distance between the user and the end office under the conditions at the time (36V is a safe voltage, and it is unsafe to exceed too much). Later, in order to be compatible with early equipment and reduce costs, the central office communication equipment still used -48V power supply.

Why is a -48v battery grounded?

In telecom the positive terminal of the battery or power supply is grounded. That makes everything powered by the -48V negative or 0 at most relative to ground, which is superior in preventing the more damaging electrochemical reactions should the circuits get wet and current leaks to ground. +1 for mentioning this, thank you!

What power supply is used in a central office communication system?

Later, in order to be compatible with early equipment and reduce costs, the central office communication equipment still used -48V power supply. Likewise, with a negative power system, the positive ground is just a convention. It turns out that there is a saying that there are a lot of negative charges in the air.

Does a voltage source have a polarity?

A voltage source is negative or positive according to how it is measured. It has no inherent polarity of its own. Only the terminals can have a polarity relative to another reference. The telecom industry uses the positive terminal of a 48-volt battery as the reference (0 volts) making the other terminal -48V.