Line Link

A line link frame (LLF or LL) is a type of frame in electromechanical crossbar exchanges that contains customer lines. It is analogous to the line finder in step-by-step and panel systems. Each subscriber occupies one vertical unit on a crossbar switch on the line link frame that is permanently tied to their telephone. On the overall switching network, calls originate from customers and terminate to customers on the line link frame.

Line link frames consist of two bays, known as primary and secondary (1XB) or line and junctor (5XB). Line link frames can usually have between 190 and 500 customers, depending on their size. Thus, there are many line link frames in an average sized central office.