How to Connect Phones to PBX

By David Curtis

Wire and connect phones to a PBX telephone system.
i phone. image by Alexander Lukyanov from

There are three basic types of telephones that connect to PBX, or Private Branch Exchange systems. They are analog, digital and VoIP telephone sets. The PBX is the electronic switching system that connects network services to telephone sets and routes calls to the desired locations. Category 5 cable allows connectivity to all three types of phones and gives you the versatility to change the types of devices in any location without replacing or modifying the cabling.

Locate the termination block for the PBX telephone system. It is usually found connected to a sheet of plywood mounted on the wall next to the phone system. It will have cables connected to it from the PBX.

Locate the areas to install new Category 5 phone jacks. Look for pathways back to the area where the termination point is located.

Mount the phone jacks to the walls in the desired locations. Surface jacks are used in existing areas and flush mount jacks are used in new construction. Use a screwdriver to install flush mount jacks and install electrical boxes for new construction.

Run Category 5 communications cable from the PBX terminal block or patch panel to each jack location. Allow 6 inches of excess cable at the jack end and enough cable on the terminal block side for proper connectivity.

Examine the terminal block. Find a pattern from existing service or locate the terminal block documentation. Remove the sheathing from the end of the cable with wire strippers and terminate the cables to the block with a punch-down tool in the proper manner. Small systems often use a modular patch panel and RJ45 connectors for station termination. Crimp these connectors onto the ends of the cables using a modular crimping tool making sure the wires are in the proper order. The blue and white pairs are considered pair 1, orange and white are pair 2, green and white are pair 3 and brown and white are pair 4.

Remove about six inches of sheathing from the cable on the jack side. Connect the blue and white twisted pairs to connection one, orange and white to connection two, green and white to connection three and brown and white to connection four. Many Category 5 jacks are color-coded, making it easy to do. Some jacks require the use of a punch-down tool, while others require a flat or Phillips screwdriver to connect the wires to the jack.

Connect the terminal side of the wiring block to the PBX services side, using either a cross-connect or Category 5 patch cable. The type of connection is dependent on the type of termination block. Analog phones use a single pair, digital phones use one or two pairs and IP phones use four pairs for connectivity.

Connect the phone into the new jack and test for connectivity.