Required Extension Number Does Not Exist When the PSTN User Dials the VoIP Access Code Through the FXO Port on the IAD

• The PSTN signal is poor.
• The IAD is grounded improperly.
• The IAD software parameters are configured incorrectly.
• The IAD software has defects.
  

Solution

1. Connect the PSTN line directly to the phone and check whether the voice quality is good.
   • If no, it can be concluded that the fault is caused by the PSTN network.
   • If yes, go to Step 2.

2. Verify that the IAD is grounded properly by referring to 3.11 "AT0 Ground Impedance Test." Check whether the fault is rectified.
   • If yes, the procedure ends.
   • If no, go to Step 3.

3. Re-configure the EC, dsp, and pstnport parameters on the IAD. Check whether the fault is rectified.

   Record signal tones on the PSTN line and check whether:

   1. There are noises. Ensure that the line is not damaged, no electric leakage occurs, IAD is grounded properly, distribution frame is connected properly, no high-power device exists around the line, and the line and electronic cables are not entangle.
   2. The signal tone of the peer end is too low. Gradually increase the value of send-gain or increase the gain pstnport attribute on the port.
   3. The DTMF signal of the peer end is standard, which needs to be determined by the peer end.
   4. DC bias occurs during recording. Run the devasi parameter set 23 <1-7> command to gradually adjust the FXO impedance.
   • If yes, the procedure ends.
   • If no, go to Step 4.

   Configure the EC, dsp, and pstnport parameters by referring to the IAD product documentation.

4. Upgrade the IAD to the latest version. Check whether the fault is rectified.
   • If yes, the procedure ends.
   • If no, go to Step 5.

5. Contact your service provider for assistance.