Extension to Cellular applications are allocated on a per station basis.
Note:
Use traffic engineering to ensure that there are enough trunks available to handle the traffic sent to the cell phones.
Extension to Cellular impacts trunk utilization extensively if a large percentage of the switch users are Extension to Cellular users. In many cases, the outbound trunk calls might not actually complete since the user can answer at the Extension to Cellular station.
The number of simultaneous call terminations towards the off-PBX station is limited to the maximum number of call appearances for each extension on the switch. However, this call limit number is usually less than the maximum call appearances. For example, Extension to Cellular users normally want the call limit at two, since most cell phones can handle only two calls at a time.