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    How to troubleshoot Comm Fail when intrusion alarm panels communicate over phone lines.

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    1.   Verify the phone line voltage reads at least 6VDC when measuring voltage across Tip & Ring or 10ma when measuring current in series with either side of the phone line.

    2.   Verify proper phone number entry.

    • Enter a phone number for the control panel to dial when communicating. The number should be entered as if dialing from a telephone. In situations where the panel needs to wait for dialtone to dial, enter a 'D' in the location where the control panel should wait prior to dialing (e.g. 9D8005551212 would dial 9 for an outside line, wait for dialtone and then continue dialing 8005551212).
    • In some cases a 2 second pause may be required. In this case enter a ‘C’ in the number to add a 2 second pause. 
      • Note, the control panel dials the programmed phone number as a continuous string. It may be necessary to call the receiver with a cell phone/test phone to determine when a pause or wait for dial tone is needed while dialing.
      • Also note that the control panel will dial the characters [#] or [*] as if they were pressed on a telephone keypad.
    • Add any number required for obtaining access to an outside line or for long distance dialing. This entry should be added in the same way as if dialed from a standard telephone (e.g. dial 9 for outside access).
    • A test may be performed by programming the panel to communicate to the phone number of a cell phone. The cell phone should ring when the panel communicates.

    3.   Verify the programmed reporting format is compatible with the receiver. For example, if the receiver only provides Contact ID ACK tones, then the control panel’s reporting format must be set as Contact ID.

    4.   Monitor the panel phone line while it sends a report.

    • Listen with a test phone for:
      • Dial tone as the communication begins.
      • DTMF tones as the panel dials.
      • Receiver Rings.
      • Receiver answers with correct ‘ACK’ tones for CID or M3a2.
      • Data transmission tones indicating the panel is reporting data.
      • Kiss-off tone to indicate the report was received.
    • If the panel doesn’t detect the receiver’s Kiss-off tone after sending data the phone line is disconnected and the panel makes another attempt to send the report. The panel makes 10 attempts to send the report and if a Kiss-off tone is not detected after the 10th attempt, it will go into Communication Fail.
      • Communication Fail is often caused by:
        • Noise or attenuated signal on the panel phone line.
        • The panel is using an internet based phone line (see below).

    Alarm panels require precise timing between DTMF tones or pulses during communication.  The characteristics of IP based phone systems (e.g. latency, codecs, etc.) may impact this timing and cause the communication to fail. Because the existing telephone system is increasingly transitioning from POTS (Plain Old Telephone System) to an internet based system, it may be difficult to know if an IP based phone system is used.

    Version history
    Last update:
    ‎12-06-2023 09:28 PM
    Updated by: