Telecommunications Generators

Telecommunications Generators

Telecommunications Generators

 

Although other voltages are possible, most radio transceiver loads used in telecom base stations run on a -48V DC bus. This practice originated in the early days of telephony, when 48V DC was found to be suitably high for long telephone lines but low enough to prevent serious injury from touching the telephone wires. Consequently, most electrical safety regulations consider DC voltage lower than 50V to be a safe low-voltage circuit. It is also practical, because this voltage is easily supplied from standard valve regulated lead acid (VRLA) batteries by connecting four 12V batteries (like those used in cars) in series, making it a simple system. The positive grounded or -48V system is another survivor from earlier industry practice. Negative voltage on the line was found to be superior to positive voltage in preventing electrochemical reactions from destroying copper cables if they happen to get wet. Negative voltage also protects against sulphation on battery terminals. Sulphation, the buildup of crystals of lead sulphate, is the leading cause of early battery failure.