Call waiting with “Caller ID” uses a special signal in
order to warn you about an incoming call, during another call there are shown the
name and number of the calling subscriber on the display. The function also
allows switching between two calls.
The service offered by telephone companies allowing creating the telephone numbers on the same line where the existing number is. The call tone for every number will be different from another. There is also an opportunity to program a custom ring tone for the incoming call.