The wonders
of Connectivity

When dealing with a private branch exchange (PBX), trunk lines are the phone lines coming into the PBX from the service provider. This differentiates these incoming lines from extension lines that connect the PBX to individual telephones. Trunking saves cost, because there are usually fewer trunk lines than extension lines, since it is unusual in most offices to have all extension lines in use for external calls at once.Trunk lines transmit voice and data in formats such as analog, T1, E1, ISDN or PRI.