What Is a Bridge Tap?

A bridge tap is a type of telecommunications connection common in residential neighborhoods, where the phone company will lay out more cable than it needs to add flexibility in the future when it needs to assign and reassign service. While this is convenient for the telecommunications company, it can cause problems for the customer, as bridge taps can come with significant interference, especially with high speed data transmissions. Customers who experience repeat problems with interference on the line that do not resolve with tactics like filtering may want to discuss the possibility of a bridge tap with a phone technician.

When phone companies lay out lines to establish connections, their goal is to make it easy to provide service to customers into the future. They can lay a long length of phone cable and use bridge tapping, if necessary, to connect various customers to that line as people move in and out of a community. Historically, multiple people were connected to one line, in the party line configuration, where households shared a phone number. With multiple lines, the company can provide full service to a neighborhood and easily switch lines if necessary to accommodate changes.

In a bridge tap setup, only one household is connected to a given line, but substantial interference can occur. The extra length of line can generate interference, depending on the length and the position of the active phone connection. This can cause issues with services like digital subscriber line (DSL) Internet service, which can be susceptible to interference. The line may also crackle or pop while people are using the voice connection.

Often, a bridge tap is visible. Customers may be able to spot the length of line and they can see that it runs continuously beyond the connection at their utility pole. On older utility poles, it is important to watch out for older lines; when a line breaks down, the phone company may string a new one without removing the old one, in which case a tangle of wires can create a misleading appearance from the ground.

A telecommunications employee can determine if a home has a bridge tap. Physical inspection can reveal the wiring used at the pole and junction box, and tools to test the line are also available. Customers with chronic Internet connectivity problems and issues on their voice lines may need to explore a number of causes before determining what is causing the problem. A phone technician may suspect a bridge tap after ruling out several other common options, and can address the problem by cutting the line, rather than allowing it to continue past the household with service.