polarity when connecting devices

Discussion in 'General Electronics Chat' started by jarwulf, Dec 26, 2013.

  1. jarwulf

    Thread Starter Member

    Jul 7, 2013
    I'm connecting a phone receiver and transmitter to a circuit board and I'm worried about polarity and potential damage issues.

    I'm going to connect the receiver and transmitter shown here which have two wires each from what I see


    through this wire



    into an 'earphone socket' on an arduino shield.


    Is there any polarity issues I have to worry about? Like for example making sure positive ends and negative ends go together or can I just connect whatever wires I want together and experiment with getting a good connection without having to worry about damage?
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    The phone system is designed to operate in a two mode or two stage process over two wires called A and B.
    By two stage I mean that the normal state of the wire is the 50 volt dial tone.
    When the handset is picked up, relays (in your pictured apparatus) or electronic switches change the mode of operation of the two wires to analog audio or pulse coded signalling.
    The means that the network saves the cost of running extra wires long distances.

    The old type of apparatus you picture will function either way round. I am not so sure about your arduino.
  3. jarwulf

    Thread Starter Member

    Jul 7, 2013
    I'm mainly concerned about potential risks to the devices. Do you think I can just experiment with connecting the wires from the devices to the intermediate wire without much risk? Is there any damage that could result to the shield? The connection is through the audio jack so it doesn't seem risky although I just want to make sure.
  4. inwo

    Well-Known Member

    Nov 7, 2013
    Neither is polarized.

    Works either way.

    Only my opinion.
    See what others say!:p
  5. jarwulf

    Thread Starter Member

    Jul 7, 2013

    do you think I'll need resistors?
  6. Athineos

    New Member

    Dec 18, 2013
    Dear friend,if your consern has to do with the polarity connection of the telephone wires i'm telling you that there is no problem.The phone line is 50V on cables.In my county line B brings the +50V.Therefore if you want with a DC voltmeter you can find out the polarity of your telephone lines.INWO is correct.You dont need resistors.Can you indicate where the tel/ne lines will be connected?