Why is 48V a telecommunications industry standard operating voltage? There are several reasons why this is the case. First, it is considered a “compromise voltage” because this voltage level is high enough to enable relatively low signal loss for transmissions over large distances and yet low enough to be considered a “safe low voltage.” Most common safety regulations internationally consider levels below 50V to be safe.
Another advantage of this voltage level is that four 12V batteries connected in series create a 48V DC backup power source, usable in the event of electrical power outage. Many central stations have elaborate arrays of 48V battery banks which may occupy even an entire room.» READ MORE