VTH number consists of 1–6 numbers, which may include
number and “#”. It must be consistent with room number
configured at the VTH.
When there are main VTH and extensions, to use group call
function, the main VTH number must end with "#0", and the
extension VTH number must end with #1, #2 and #3. For
example, if the main VTH is 101#0, extension VTHs must be
101#1, 101#2…