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Thread: How a phone center office still generate power to rj-11 port when breakdown?

  1. #1
    DIY Junior Member jonathan's Avatar
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    Unhappy How a phone center office still generate power to rj-11 port when breakdown?

    hi all,

    as we know the rj-11 which generate 48DV voltage from the center office.
    even when our house electricity break down we still can make call.
    if the center office also break down ? does the rj-11 still supply power to our phone? how does it work ? my lecturer say it still can make call! but where does the energy came from ? does the rj-11 can store enegy for a long duration? or the center office have a very large power generator ? if got a generator it support to MIllion of people at once ? i think that is impossible. OR maybe center office there got many capacitor attach to the rj-11 port circuit....

    i'm really confuse at it ... can someone give me a guidance ?
    Last edited by jonathan; 12-03-2009 at 05:07 PM. Reason: not complete sentence

  2. #2
    Plumber jimbo's Avatar
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    BATTERIES. Phones systems have always operated on batteries!

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    DIY Junior Member jonathan's Avatar
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    emmm ...jimbo .... u mean the batteries is in the phone or the rj-11 port got battery inside ? if u mean the batteries for the phone, then is not i wanted. because i mean the old fashion phone without display or any other function. just for normal call only.

    if u mean the battery is inside the rj-11 port.... mean got battery inside work like capasitor ? / or maybe the battery is at the center office side.

  4. #4
    Flipper (house)
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    The phone system runs off a battery system. The batteries are at offices thorough the country and have back up AC or DC generators depending on the office setup.

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    Plumber jimbo's Avatar
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    The power is in the central office. The 48 volts DC, or 32 volts DC in centrex systems, comes through the wires to your house, where it powers the electronic circuits in your phone. Of course, any kind of phone which requires plugged in to AC power at your house to run its electronic feature circuits, such as cordless phone, answer machine, etc.....THESE will not work without the AC line power in your house.

    That is why it is good to keep one regular plain old phone in the house, so when the cordless won't work, and the cell phones won't work, there is a good chance your plain old phone will work.

  6. #6
    Master Plumber Redwood's Avatar
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    Here's some batteries at the phone company...


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    Homeowner Thatguy's Avatar
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    Quote Originally Posted by Redwood View Post
    Here's some batteries at the phone company...

    Can you imagine shorting this array? It would probably melt a crowbar. Violently.

  8. #8

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    Great photo. I used to do all of the power cut ins for these battery banks in phone company co's. They only allow cut ins between 12a-6a to minimize the risk of losing phone service. There are backups of backups of backups inside most phone company co's. Many large city buildings have no windows for security purposes.
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

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    DIY Junior Member jonathan's Avatar
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    thx jimbo and reawood.... never thought have those battery bank at all =D

  10. #10
    DIY Senior Member thassler's Avatar
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    Quote Originally Posted by Thatguy View Post
    Can you imagine shorting this array? It would probably melt a crowbar. Violently.
    I witnessed a dropped crescent wrench at one of these at a telco. It landed across 2 copper bus bars completing the circuit. It turned a spectacular color of white before melting.
    TreyH
    ** Not a professional - only a DIYr **

  11. #11
    Plumber jimbo's Avatar
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    I am a little surprised at the photo, unless I can't see well. Are all those racks just bare steel? Light fixtures open to atmosphere??

    On submarines, we have a bank of 125 batteries. Each cell is about the size of 8 of those in the picture. The entire battery compartment is specially treated oak battens, and everything metal is coated with a heavy coating of plastisol. No metal goes into the compartment. You leave your watch, belt buckle, etc at the entrance hatch. All tools needed are specially coated and kept in the compartment. Light fixtures are of the explosion proof rated type. Hydrogen is nasty!

  12. #12
    Retired Defense Industry Engineer jadnashua's Avatar
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    Hydrogen in a sealed up submarine verses a building where you could vent to the outside are two different animals. Big problems if the ventilation fails, though, in either case.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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