Finding The Telephone Lines

In most cases, the telephone company delivers the telephone numbers for a business to a specific location called an RJ21x or the Demarcation point. "Dmarc" for short. The RJ21x normally has an orange cover with DMARC or RJ21x written on the front. In residential areas the RJ21x is normally located in a gray box on the outside of the residence. In a business office the RJ21x is normally in an equipment closet or maintenance or electrical room.

In order for a telephone system to work, the telephone lines from the RJ21x must be connected into the KSU (Key Service Unit) of the telephone system. In most cases it is a good idea to install the phone system as close as possible to the RJ21x. If this is not possible, cables may have to be run from the RJ21x to wherever the telephone system's KSU has been installed.

Once the RJ21x has been identified, the lines can be connected to the telephone system. A telephone line consists of two wires. These wires are referred to as "Tip" and "Ring". Normally, the Tip and Ring for a telephone line is terminated on the far left, or first column of pins on the RJ21x. The Tip is terminated above the Ring on the block.

Bridging clips, the small, metal rectangular clips are used to connect the left side,or phone company side of the RJ21x to the right side or customer's side of the RJ21x. These clips are used for troubleshooting purposes. If a telephone line has static on it, a technician can remove the bridging clips associated with that line. Which isolates the line from anything connected to the customer's side. If the static remains on the line, the technician knows the problem is not with the customer's equipment or wiring but somewhere on the phone company's side, either in the phone company's central office or in the copper wire running from the central office to the RJ21x.

It is important to know where the telephone numbers being connected to the telephone system are located on the RJ21x. It is also helpful to know if the numbers are in a rotary group (hunt group), and the order in which they roll (hunt). A rotary group (hunt group) consists of several phone numbers, grouped together by the telephone company. When one of these numbers is busy, the phone company sends subsequent callers to the next phone line in the hunt group. When connecting phone lines in a hunt group to a telephone system it is a good idea to connect the first phone number as line 1, the second number as line 2, etc.