This attribute displays the operational mode of every time slot
which is serviced by a voice service.
The value idle means that the time slot is not used to service a call,
hence the concerned voice service's bandwidth in the Passport
subnet is available for other uses.
The value voice means that a phone call is in progress. All
provisioned voice service's value added features have been activated
(features such as voice compression, silence suppression, echo
cancellation).
The value data means that a data call is in progress. All provisioned
voice service's value added features have been de-activated, so that
a clear 64 kbit/sec data connection is provided accross the Passport
subnet.