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PHONE LINE MANAGER 16 X 4
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12.2 Disconnect Supervision: Polarity Reversal/Clear Forwarding
Some Central Office switches signal the unit when the remote party in an outside call has disconnected from
the line. For example, if an outside call is placed on hold and during that time the outside party hangs up,
the system will know to release the line. The Phone Line Manager 16 x 4 supports two types of signaling.
With Clear Forward signaling, used mostly in the USA, the Central Office removes the battery feed from the
Tip and Ring lines to signal that the remote party has disconnected. With Polarity Reversal signaling, the
Central office reverses the polarity of the Tip and Ring signals to inform the unit when a connection has
been completed and when it has been disconnected. If a disconnect signal is detected during an outside line
conversation, the extension hears special tone (on for 1 second, then 2 brief beeps, then the system dial
tone) to indicate that the call has been disconnected.
If you are being inappropriately disconnected from outside calls, disable both of these parameters.
To Enable Polarity Reversal Detection:
1. In programming mode, enter 7844. Pause for confirmation tone. Hang up or continue with
programming.
To Disable Polarity Reversal Detection:
1. In programming mode, enter 7845. Pause for confirmation tone. Hang up or continue with
programming.
When Polarity Reversal detection is enabled, the Phone Line Manager 16 x 4 software will only store the
details of an outgoing call into Call History memory if the first polarity reversal is received, indicating that
the connection to the called party is made. Thus if an outgoing call is made and the called phone rings for
longer than 20 seconds but never answers, the call is not recorded.
To Enable Clear Forward Detection:
1. In programming mode, enter 7820. Pause for confirmation tone. Hang up or continue with
programming.
To Disable Clear Forward Detection:
1. In programming mode, enter 7821. Pause for confirmation tone. Hang up or continue with
programming.
There are 4 DIP switches on the Trunk Board of the Phone Line Manager 16 x 4 which must be set in the
“Up” or “Off” position to allow Polarity Reversal to be detected or in the “Down” or “On” position to allow
Clear Forwarding to be detected.
If the DIP switches on the Trunk Board are set differently from the system software setting, improper
operation will result.
If the System Manager inadvertently configures the system to detect both the Polarity Reversal and the
Clear Forwarding signals, the system software will look only for the Polarity Reversal signal.