Sony ID Telephone IT-ID80 Mode D'emploi page 20

Using "Caller ID with Visual Call
Waiting" service
This telephone is compatible with the "Caller ID with Visual Call
Waiting" service. Make sure that your telephone company offers this
service.
Like the basic Caller ID service, you need to subscribe to "Caller ID
with Visual Call Waiting" in order to use this service.
Even though you may have already subscribed to "Caller ID" and
"call waiting" as two separate services, you need to request a
subscription to "Caller ID with Visual Call Waiting" as a single
service.
This is a new service that combines the two services.
Even though you now have a "Caller ID with Visual Call Waiting"
compatible phone, unless you subscribe to the combined "Caller ID
with Visual Call Waiting" service, you will not be able to see the
name and number of the second caller.
When a new call comes in while you are talking, "CALL WAITING"
appears on the display and then the caller's name and/or phone
number of the new call appears on the display for about 20 seconds.
To switch to another caller
EN
20
Caller ID Features
1
To switch to the new caller,
press (CALL WAITING/FLASH).
2
To switch back to the first caller,
press (CALL WAITING/FLASH)
again.