A split pair is a wiring error where two wires from different twisted pairs are yoked together, potentially creating interference. Telecommunications wiring is most commonly configured using the twisted pair technique, and a split pair can cause problems like crosstalk on a phone line or interference with a video signal. These problems can indicate a wiring issue and may prompt a technician to check for signs that pairs could have been split while connecting telecommunications interfaces.
In a twisted pair, two conductors are wrapped around each other to reduce interference along the line. It is common for a number of twisted pairs to be wrapped together in a single heavily insulated cable to carry a variety of signals. For instance, a phone line to a house might have three twisted pairs, AB, CD, and EF. Each twisted pair needs to connect to the right circuit, or interference will develop.
When someone makes a wiring error and creates a split pair, the pairs are broken up and wired across each other. For example, a phone technician might connect A to D and B to C, while EF might be left intact to connect to the right point of contact. Someone using phone or video transmission services would notice problems caused by the twisted pair. Testing of the line could show that the signal is good from the telecommunications company, so the problem can be found in the internal wiring.
Twisted pairs are typically color coded to make it easier for technicians to work with them. They can avoid twisted pairs by doublechecking before making any connections, and in some cases may also tag wires to make their functions especially clear. People are usually advised to leave twisted pairs alone to avoid the creation of wiring problems, and when service is required inside a home or office, where the utility is not responsible, tenants need to exercise care if they work on their lines.
Electrical testing can be used to check for a split pair. Wires paired at a junction or other connection should behave like twisted pairs. If they do not, it suggests that they are actually split pairs. Technicians can use electrical testers to check on the line before they close up a junction and pronounce a job finished. The same equipment can be used to quickly check if a customer reports a problem that sounds suspiciously like a split pair.