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Thread: How to test phone line with DMM

  1. #1
    Join Date
    Jul 2009
    Posts
    56

    How to test phone line with DMM

    I have a problem with my modem, i think. Am No dial tone on a telephone line that usually works fine. Originally I had this problem only when a modem picked up to dial and not when I picked up a telephone on the same line, but I started to when it may also record a telephone. The problem comes and goes in unpredictable times. Does Anyone of you knows what specific electrical tests may be the quality of a telephone line measurement, and what values should expect to receive? Is there any way i can test phone line with Digital Multimeter ?

  2. #2
    Join Date
    Nov 2005
    Posts
    2,327

    Re: How to test phone line with DMM

    Selecting and configuring a DMM requires preliminary analysis in two broad areas, that is the device under test and the test environment.the DMM must have a wider measurement range than the expected minimum and maximum test signals. To test a phone set, when onhook A "telephone set" should measure virtually an infinite resistance and when it is offhook, it should be less than 325 Ohms. Similar to test a telephone line it should have virtually 0 current when connected to an onhook telephone and when connected to an offhook
    telephone it should have more than 23 MA.

  3. #3
    Join Date
    May 2008
    Posts
    1,818

    Re: How to test phone line with DMM

    DMM should have the line voltage and frequency testing where you work. However, if you have an instrument model that different countries should be used standardizes, the other power standards support. A universal power supply that the sense voltage and frequency automatically avoid problems that could arise as a DMM power switch must be manually placed. You can use a battery option for portable applications like. Also check the power consumption in cooling the extra material you need shelving.

  4. #4
    Join Date
    Feb 2009
    Posts
    161

    Re: How to test phone line with DMM

    The flow of the line would actually never have exceeded 60 mA, but it could be as much as 120 mA and within specifications. At this flow, a resistance of 325 ohms just 5 Watts away. But at 45 mA, which is probably the highest flow line is you will ever see will be just under 1 / 2 Watt heat production.

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