The External Line Select feature on attendant consoles and supported Mitel IP Phones allows the attendant to seize a nominated analog or digital trunk and dial digits over it in order to verify the trunk's "serviceability". The attendant identifies the trunk by its associated 4-digit trunk number.
The following phones support the External Line Select feature: 5020 IP Phone, 5220 IP Phone and 5220 IP Phone (Dual Mode), 5224 IP Phone, 5312 IP Phone, 5320 IP Phone, 5324 IP Phone, 5330 IP Phone, 5340 IP Phone, 5360 IP Phone, and Navigator.
There are no conditions, programming, or operation instructions for this feature.