B) In some cities, it costs less to bring a group of direct inward dial or combination trunks into your premises over a T-1 than to bring them in separately, each over a separate pair of copper wires. The Telecom Handbook of 219 Figure 10.6A T-1 from the Local Telephone Company Central Office Using T-1 Circuit Board In PBX 4 Wire T-1 Circuit Carrying 12 DID Trunks and 12 Combination Trunks (24 Channels) T-1 Circuit Board Local Telephone Co. in PBX Central Office Figure 10.6B T-1 from the Local Telephone Company Central Office Using Channel Bank 12 DID Trunks DID Circuit Boards 4 Wire T-1 Circuit Carrying 12 DID Trunks Combination Trunk and 12 Combination Trunks Circuit Boards (24 Channels) 12 Combination Trunks Local Telephone Co. Central Office OUTSIDE LINES For example, in New York City a DID trunk costs about $75 per month, SO 10 will cost $750. For that same $750 or less, twenty- four DID trunks can be brought into your PBX on a T-1 circuit (This includes the cost of the T-1 and the cost of the DID). In this instance, the other end of the T-1 is at the central of- fice of the local telephone company. They are responsible for the multiplexing capability at their end. Telephone companies may give this type of a T-1 a different name for marketing purposes such as Flexpath which is used in New York City. T-1 to Connect Two Offices of the Same Organization (Figure 10.7) Another common use of a T-1 is to connect two locations of an organization. This may be used for 24 tie lines connecting 2 PBXs or it may be used for a combination of voice and data cir- cuits. In the latter case, it is advisable to terminate the T-1 in a multiplexer external to the PBX. It is likely that the people using it for data will need to monitor the line and may want more so- phisticated diagnostic capabilities than are available when the T-1 terminates on a T-1 circuit board in the PBX. Again, the local telephone company may have a marketing name for this type of T-1 such as Superpath, used in New York City. T-1 to Your Long Distance Carr