Numbering

Numbering Plan

When planning the numbering plan for the site to be installed, it is important to examine the existing telecom environment and what the customer requires.

This section only mentions the most important items to think about.

For detailed information about numbering see operational directions for NUMBERING.

Public Numbering plan

Direct in-dialing requires that a number range in public network have to be subscribed from the Telecom operator if not already available. Make sure that the subscribed public number range is sufficient for the present installation and planned expansion.

Internal Numbering plan

If direct in-dialing is used the internal numbering must be adapted to the subscribed number series.

The size of the system may have an influence on the number scheme used for internal dialing. It is possible to choose between 2 to 20 digit numbers for extensions. One digit numbers can be used for Hospitality.

After having decided upon the length of the extension numbers, make a plan on how the internal numbering plan should be used:

• Call number to Operator Group and to the individual Operator.
• Call number to PSTN
• Call number to the Private network if applicable
• Call numbers to groups, for example, Group hunting groups
• Number series for Speed dial numbers (Abbreviated Dialing)

Customer Numbering plan

Customer numbering plan provides an ability to give multiple groups of users in the system their own dialing plan, e.g. multiple groups of users can have the same local dialing plan consisting of the last 2-5 digits of the system numbering plan.

For calls to other user groups, a complete system number must be dialed.

The primary scenario for the feature is when a private network is collapsed into a single system. The users can continue to use the existing dialing plan, e.g. if the network dialing plan was location code based, the users would still dial the short local number and use the location code prefix to dial other locations.

In the system, the users are defined with the long numbers, i.e. including the location code.

For new installations where locations would like to use part of the system numbering plan for local calls, it is recommended to use the last digits of the public listed directory number including the area code as system number.

Existing System

Is there a need to adapt the numbering plan to the numbering used by a previously installed telephone system? The users might want to keep their existing directory numbers.

Make a list of the existing numbers that should be used in the new system.

Trunk Call Discrimination

It is possible to create a table in the system with public or private network (mostly expensive) destinations, for example, international calls or pay-per-call services, that should be opened or blocked for certain extensions in the system. It is good to create a list of these destinations already in the planning stage.