# Calling line identification restriction (CLIR)

The CLIR service is used with the CLIP service. The CLIR service blocks calling party address information from being presented to the called user.

This service is available under many variants, including Q.SIG.

The CLIR service can be provided in either permanent or temporary mode.

- Permanent mode: Usually provided to the calling user on a subscription basis. Prevents the calling user's address information from being presented to called users.

- Temporary mode: May be provided to the calling user on a subscription basis or may be generally available. Allows the calling user to decide, on a call-by-call basis, whether to allow the called user access to the calling party address information. When subscribing, the user can specify a default behavior:

Default behavior | Description
Presentation restricted | By default, the network blocks the calling user's address information from the called user.
Presentation not restricted | By default, the network allows the calling user's address information to be presented to the called user.

The calling user can override either default on a call-by-call basis.

If the calling user has subscribed to CLIR in temporary mode, the application determines if the called user can access the address information by setting the Acu_conn_rq_calling_nb_pres macro in the ACU_CONN_RQ message. If the calling user sets Acu_conn_rq_calling_nb_pres to N_PRES_ALLOWED, the called user can access this information. If the calling user sets Acu_conn_rq_calling_nb_pres to N_PRES_RESTRICTED, the information is denied the called user. In this case, calling line information is not included in the ACU_CONN_IN primitive.

Note: A subscription option exists which causes presentation restricted to be overridden.

## CLIR and other services

This section describes the interaction between the CLIR service and other supplementary services.

### Call diversion, call deflection

If the CLIR service is active, the calling party's address information is not presented to the diverted-to user unless the diverted-to user has the CLIR override subscription option.

### Explicit call transfer

The calling user's restriction requirement from the original call is used to restrict the presentation of that user's address information to the transferred-to user.