Wiring Connections: Hooking Things Up

The telco uses a variety of connections to bring the service to the customer locations. The typical connection is the two-wire service that we keep talking about. This two-wire interface to the network is terminated in a demarcation point as required by law. The DEMARC is the point of least penetration into the customer’s premises, typically within 12 of where the telco cable comes up into the building. Normally, telco terminates in a block; this can be the standard modular block for a single-line telephone. If the customer has multiple lines, telco will terminate in a 66 block, or an RJ21X. These are fancy names for their termination points.

The typical modular connector uses an RJ11C for telephones connected to a 2-pair interface (not to be confused with the two wires), or an RJ45X as a 4-pair interface for both voice and data. Another version of connector for digital service is an 8-conductor (4-pair), called the RJ48X.

When a telco brings in a digital circuit, it will terminate the 4-wire circuit into a newer RJ68 or a smart jack. There is no major mystique in any of these connectors. The number is strictly a uniform service code so that they can keep it all straight. However, when ordering a circuit, the telco will ask you how you want it terminated. The rule of thumb, in a multiline environment, is to use the RJ21X (which is a 66 block with an amphenol connector on it). Sounds complex, doesn’t it? A single line will terminate in an RJ-11C or RJ-12.