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  1. derid

    AC voltages on analog lines

    The schematic diagram is on : http://www.electronic-design.be/downloads/data/trunk.pdf When on hook, K1 is off and the ringing voltage goes trough R13/C9. The ac voltage at "AUDIO" is detected by the ADC of the microprocessor as a call. It looks like there is always a signal at "AUDIO" once...
  2. derid

    AC voltages on analog lines

    It is powered bij 12Vac or 13.8Vdc and can be installed either on a POTS line or a PBX The circuit is isolated from the trunk by means of a 600 Ohm transformer More info on : http://www.electronic-design.be/en/htm/body/parlofonie/tpi+/TPI+GB.pdf
  3. derid

    AC voltages on analog lines

    I do have an oscilloscope but the cable of my probe is unfortunately a little bit too short : I'm living in Europe !!! I am a telecom designer. A few weeks ago I sent a doorphone interface to the States. That interface can make a doorcall to a local phone or to a remote phone through a trunk...
  4. derid

    AC voltages on analog lines

    Thank you for your answers. Of course there can be ringing voltage and there can be losses too. The question was in normal conditions and idle mode are there some other AC voltages like : - FSK or DTMF modulation for CLIP - carrier frequencies to get 2 channels on one twisted pair -...
  5. derid

    AC voltages on analog lines

    Can someone tell me if there are AC voltages present on an analog line(PSTN) in idle mode in the USA ? for example (FSK modulations, carriers, tones etc...) What is the maximum allowed noise amplitude on such a line ?

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