US T1 Line

Last Updated : Aug 30, 2026 |
Navigation: System SettingsLineUS T1 Line
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Resource Id: line133
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Field
Description
Line Number
Allocated by the system.
Card/Module
Indicates the card slot or expansion module being used for the trunk device providing the line.
For IP500 V2 control units: 1 to 4 match the slots on the front of the control unit from left to right.  Expansion modules are numbered from 5 upwards, for example trunks on the module in Expansion Port 1 are shown as 5.
Port
Indicates the port on the Card/Module above to which the configuration settings relate.
Network Type
Default = Public.
This option is available when System | Telephony | Telephony | Restrict Network Interconnect  is enabled. It allows you to configure trunks as either Public or Private.
  • The IP Office will return number busy indication to any attempt to connect a call on a Private trunk to a Public trunk or the opposite.
  • The call restriction includes transfers, forwarding and conference calls.
  • Avaya does not recommended use of this feature on IP Office systems using any of the following features:  multi-site networks, VPNremote, application telecommuter mode.
Line Sub Type
Default = T1
Set to T1 for a T1 line.
Channel Allocation
Default = 24 | 1
The order, 24 to 1 or 1 to 24, in which channels are used.
Prefix
Default = Blank
Enter the number to prefix to all incoming numbers for callback. This is useful if all users must dial a prefix to access an outside line. The prefix is automatically placed in front of all incoming numbers so that users can dial the number back.
Framing
Default = ESF
Selects the type of signal framing used. The options are:
  • ESF
  • D4
Zero Suppression
Default = B8ZS
Selects the method of zero suppression used. The options are:
  • B8ZS
  • AMI ZCS
Clock Quality
Default = Network
Refer to the IP Office Installation Manual for full details. This option sets whether the system should try to take its clock source for call synchronization and signalling from this line. Preference should always be given to using the clock source from a central office exchange if available by setting at least one exchange line to Network.
  • If multiple lines are set as Network, the order in which those lines are used is described in the IP Office Installation Manual. If additional lines are available, Fallback can be used to specify a clock source to use should the Network source not be available.
  • Lines from which the clock source should not be taken should be set as Unsuitable.
  • If no clock source is available, the system uses its own internal 8KHz clock source.
  • In scenarios where several systems are network via digital trunk lines, care must be taken to ensure that all the systems use the same clock source. The current source being used by a system is reported within the System Status Application.
Haul Length
Default = 0-115 feet.
Sets the line length to a specific distance.
Channel Unit
Default = Foreign Exchange
This field should be set to match the channel signaling equipment provided by the Central Office. The options are:
  • Foreign Exchange
  • Special Access
  • Normal
CRC Checking
Default = On
Turns CRC on or off.
Line Signaling
Default = CPE
This field affects T1 channels set to Loop-Start or Ground-Start. The field can be set to either CPE (Customer Premises Equipment) or CO (Central Office). This field should normally be left at its default of CPE. The setting CO is normally only used in lab back-to-back testing.
Incoming Routing Digits
Default=0 (present call immediately)
Sets the number of routing digits expected on incoming calls. This allows the line to present the call to the system once the expected digits have been received rather than waiting for the digits timeout to expire. This field only affects T1 line channels set to E&M Tie, E&M DID, E&M Switched 56K and Direct Inward Dial.
CSU Operation
Enable this field to enable the T1 line to respond to loop-back requests from the line.
Enhanced Called Party Number
Default = Off
This option is not supported for systems set to the United States locale. Normally the dialed number length is limited to 15 digits. Selecting this option increases the allowed dialed number length to 30 digits.
Admin
Default = In Service.  
This field allows a trunk to be taken out of service if required for maintenance or if the trunk is not connected.
Related links
T1 Line