# Notify retrieve

The notify retrieve operation notifies a remote user of a call retrieve operation involving the user.

## Notify retrieve (ETS 300)

In an ETS 300 configuration, the stack performs this operation to notify the application when the remote equipment has changed the auxiliary state of a local subscriber to retrieved. An acu_ss_notify_retrieve_invoke extended data structure is sent to the application in an ACU indication message.

## Notify retrieve (Q.SIG)

In a Q.SIG configuration, the application at one node performs this operation to notify the application on a remote node when a call previously on hold has been retrieved. To do so, it sends an acu_ss_notify_retrieve_invoke extended data structure to the application in an ACU request message.

The following illustrations show the message types interchanged between the stack and a Q.SIG application when the notify retrieve service is invoked from the perspectives of the local node and the remote node:

Local notify retrieve

Remote notify retrieve