What is a volts direct current signal as it relates to telecommunications?
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Negative 48 volts direct current (-48VDC) is typically found on landlines in an idle state. When someone calls a phone number, an AC current of 90 volt-ampere current (90 VAC) is applied to the loop to make the phone ring. The term -48VDC is typically referred to as talk battery in the worlds of plain old telephone service, or POTS, and public switched telephone networks, or PSTNs. From here, the volts direct current expands to channel banks, multiplexers and numerous other wares. Volts direct current is found in numerous technologies because digital gear often deals with stepped-down and lower-DC voltages than a typical AC house current.
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This was first published in January 2014