0
always think of any supply system so :
RED = MOST POSITIVE
BLACK = MOST NEGATIVE
in a telecom system the -48V supply is refferenced to ground and earth, so the supply wire is NEGATIVE,
this means a DC supply most positive signal the RED wire, go to EARTH = ZERO,
the BLACK wire is the MOST negative, so in this case it is -48V
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How do you get -48v DC?
In a 48V DC system you ground the positive to 0V so the live wire will be -48V.
Why use -48V dc in bts?
-48 v is given to BTS because in this voltage Noise generation is minimum. Because two terminal comes out from the battery and through red color wire we ground the +ive terminal so that possibility of noise interference will get zero because noise occurs only in the +ive terminal that's why we use -ive voltage in the BTS.
Why is a rectifier needed for a GSM BTS?
This is bcoz we need -48V for Gsm BTS, -48 DC is used to control Fluctuation So the main function of this is 1) To convert AC to DC 2) To control overloading
What is a multiply contact relay?
It is a type of relay used to read the status of Breakers as well as isolators in scada system. As RTU operates at a voltage of 48V and Control panel operates at 110v inoredr to differentiate these potentials it is used
Why DC is preferred in telecom industry?
One main advantage is that it is easier, cheaper, and more efficient to battery back the system. -48V DC can be made simply of 4 12V batteries (think giant car batteries) in series. The string looks like this: AC POWER --> RECTIFIER --> BATTERIES --> DC LOAD To battery back an AC system you have this string. AC POWER --> RECTIFIER --> BATTERIES --> INVERTER --> AC LOAD (which is usually converted back to DC by the equipment's power supply to run the electronics). No step in this process is 100% efficient, and every part costs $$. DC eliminates a lot of these steps. This is not to say that everything in a Central Office is DC powered -- they still have Air Conditioning, Lights, convenience outlets, etc -- but if you're ever in a Central Office when the power goes out, those things turn off until the generator kicks on and the transfer switch swings. Also -- doing things with Low Voltage (-48V) does have some EXPENSIVE costs associated with it. COPPER power runs are very expensive because of the low voltage used (-48VDC) -- it takes more than twice as much copper to feed the same Wattage/Amperage as a 120V supply. A=V*W W=V/A V=W/A The simplest rating on a wire is how many A it can draw for how many feet (there are other ratings, such as maximum voltage, but most of these approach 600V, so don't apply to this comparison). Most of these additional costs are one-time costs and therefore are justifiable.
