BusinessPhone Communication Platform 4.0
Facilities

## ISDN SS Calling Line Identification Restriction (CLIR)

## Definition

The supplementary service CLIR enables the calling party to prevent presentation of its ISDN number to the called party.

## Use

For outgoing external calls this feature is used to conceal one’s own identity from the called party.

## Operation

### Outgoing calls

#### System telephones

There are two alternatives at outgoing calls to restrict the representation of the A-number at the B-party (number secrecy).

##### Permanent mode

Command 0149 number secrecy = YES

The extension is configured to always restrict the presentation of the A-number. At call setup, BTU-D / BTU-B_ / MFU informs the public network to restrict the A-number at the B-party.

##### Temporary mode

Command 0149 number secrecy = NO

A “number secrecy“ key can be programmed at system telephones, and the user himself may decide whether or not to restrict the presentation of A- number at the B-party.

This key is at the same time also used for the COLR- function described in a later chapter. For A-number restriction at the B-party, the key “number secrecy” has to be activated before call setup. Restriction is activated until the key is pressed again.

LED-status of the key “number secrecy”:

- Extinguished = A-number is presented at the B‑party.
- Steady light = A-number is restricted at the B-party

Note

No matter which mode - temporary or permanent - is activated, it will always have an effect on a subscribed COLR function (see ISDN SS Connected Line Identification Restriction (COLR))

#### ISDN terminals

By programming it is defined whether or not ISDN terminals on the S-interface are allowed to use the CLIR/COLR function, how the CLIR function will be activated, depends on the terminal type used (see User’s Guide).

### Incoming calls

#### System telephones

If the A-party has activated CLIR, the A-number is restricted and a special information is presented on the display of STANDARD, EXECUTIVE and OPERATOR telephones.

#### ISDN terminals

It depends on the terminal type used, how number suppression will be shown on the ISDN terminals (see User’s Guide).

If CLIR is activated by the calling party, the calling party number will not be shown at the display of the called party, however the calling party number is still available in the public network. In case of malicous calls it is possible to register the calling party number by using the supplementary service MCID (Malicous Call Identification). Once registered, the calling party number of a specific malicous call can easily be requested from the public network provider.

Especially in case of calls to emergency numbers (police, ambulance, fire brigade, ...) it is important that the number restriction of the calling party number can be overridden. In some countries the public network supports this functionality by providing the calling party number to the called party whereby the number information is still marked as not to be used for display purpose due to activated CLIR service.

Depending on the programming (command 1948), it is possible to define whether or not an activated CLIR service will always be overridden and the calling party number presented on the display.

## Capacity/Limitation

If permanent mode is activated (command 0149 number secrecy = YES), the key “number secrecy“ does not have any function and the lamp lights.

## Programming

The commands necessary for A-number restriction at the B-party are also used by the supplementary service COLR.

0101 |  | Facility COS

3050 |  | Program number secrecy key

0301 |  | Key function

0149 |  | Number secrecy to public network ?

0169 |  | Directory number subscribed in PSTN ?

1948 |  | CLIR Override at incoming calls

### ISDN terminals

1957 |  | Number restriction allowed from TEs ?

## Equipment

BTU-D with ISDN prom set or BTU-B_ or MFU.

Revision: H © Ericsson Enterprise 2003