The data rate to use for active calls based on this call details entry. The actual data rate for outgoing calls
is determined by both this object and the data rate parameter for the Q.931 interface chosen for the call. If
either this object or the interface object specify a rate of 56k, then 56k will be the rate for the call.
Otherwise, the default rate of 64k will be used. This allows interoperability between ISDNs which only allow 56k
of data on a B channel.