What Is a Distribution Frame?

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  • Written By: Paul Scott
  • Edited By: E. E. Hubbard
  • Last Modified Date: 25 November 2019
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A distribution frame is a passive connection system used to terminate and interconnect telecommunication and audio-visual cable systems. These components typically consist of groups of connection blocks mounted on vertical racks within a dedicated enclosure, kiosk, or building. The blocks are usually of a double-sided design that allow for an incoming, or feed, cable to be connected to one side and an outgoing, or consumer, cable to be interconnected with it on the other side. The connections are generally made using a special tool that pushes the wire down into the connector block, simultaneously stripping the insulation and securing the connection. The distribution frame allows these interconnections to made, removed, and changed at will as the need arises without disturbing any of the other existing connections.

Cable telecommunication and broadcasting networks make use of large numbers of cable pairs typically consisting of incoming feed and outgoing consumer cables. In a telecommunication network, available lines are routed out of a central exchange to secondary distribution points where they are then connected to consumer's home lines. In the exchange and secondary distribution points, a distribution frame system is usually employed to facilitate these connections. These systems consist of modular, insulated connector block units mounted on a vertical panel, rack, or backing board. The distribution frame may contain anywhere from a single to several hundred connector units depending on the size of the network that it serves.


The connector units used in the frames are double-sided and consist of a number of back-to-back connection points. They most often resemble a large slab of chocolate with a series of blocks on the left and right sides of the unit. Each left and right pair are interconnected with a bus link and feature a separate stab-type connection point on each side. In most cases, the left side of the unit will be used for incoming feeds and the right side for the consumer lines.

In the case of an empty, unpopulated connector, a typical interconnection will be made in the following manner. The two wires of the incoming line from the exchange for a specific telephone number will be connected to the number one and two blocks on the left hand side of the connector unit. The two wires of the user's line will be connected to blocks one and two on the righthand side. The connection bus between the left and right sides then ensure that continuity is established between the feed and consumer lines. Each new connection will occupy the next two free rows of connectors.

The individual connector units differ in size and may consist of 12 connection points or more. The number of connector blocks used in the distribution frame will also depend on the size of the network that the frame serves. This system allows linesmen or technicians to easily test a specific line and to make new connections and remove existing ones without interrupting the service to any of the other lines.


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