BusinessPhone Communication Platform 4.0
Facilities

## Trunk Call Discrimination (TCD)

## Definition

Using Trunk Call Discrimination = TCD it is possible to determine (program) to which area (routing number) codes the extensions shall be permitted to ring.

Also incoming trunks can be checked.

Permitted area codes are placed in a table and assigned to one or several TCD Class of Services.

At outgoing calls from an extension or trunkline, it will be checked according to the related TCD Class of Service, which external numbers are allowed to be dialled.

## Use

TCD provides the possibility, in a flexible manner, to restrict the possibilities of extensions to make expensive calls.

## Operation

For outgoing external calls each dialled digit is compared with those number intervals that, are to be checked in accordance with the extension's or trunk's TCD Class of Service.

The check is made according to the following rules:

- Dialled digit exists in the table.

- No more digits are to be checked.
- The destination is open, TCD is disconnected.

- Dialled digit exists in the table but the entry in the table consists of more digits.

- More digits are to be checked.
- Wait for more digits.

- Dialled digit doesnot exist in the table.

- The destination is blocked.
- The trunk will be disconnected and marked free. The direction is blocked for the caller who receives congestion tone.

## Capacity

Permitted destinations are stored in a table compiled on the basis of number intervals.

A number interval can be two arbitrary digit combinations, where digit combination 1 must always be lower or equal to digit combination 2.

Example of number intervals

- 1-6
- 71-79
- 01234-01238
- 00942-00942

If a number interval is programmed as 2-4, this means that all destinations that begin with 2, 3 or 4 are open.

100 number intervals (00-99) can be programmed.

Each number interval can have a discrimination depth of up to ten digits.

Extensions and trunks can be assigned one of nine TCD-categories (0-8) for day traffic and night traffic. If an extension or a trunk is assigned category 0 this means that no check will be undertaken.

For each number interval is stated in which of the TCD-categories 1-8 the interval is permitted to be dialled.

When the system is switched for night service, the check (comparison) is made against those intervals that correspond to the night service categories, otherwise against the day service categories.

## Limitations

Extensions belonging to group 0 are fully open for external traffic, that is they are not subjected to TCD-analysis.

External numbers not entered in the table are blocked for all extensions except those with category 0.

Calls made with the help of common abbreviated numbers are not checked by the TCD, whereas individual abbreviated numbers are.

## Programming

### TCD-table programming

2201 |  | Open number interval

2202 |  | Open for TCD category 1

2203 |  | Open for TCD category 2

2204 |  | Open for TCD category 3

2205 |  | Open for TCD category 4

2206 |  | Open for TCD category 5

2207 |  | Open for TCD category 6

2208 |  | Open for TCD category 7

2209 |  | Open for TCD category 8

### Extension programming

0103 |  | TCD-day COS

0104 |  | TCD-night COS

### Trunk programming

Following commands are only accessable via BMS/RASC:

1003 |  | TCD-day COS

1004 |  | TCD-night COS

1015 |  | Pre-digits for number analysis

## Equipment

None

Revision: D © Ericsson Enterprise 2003