Telephone exchange distribution frames

摘要

In a telephone exchange, the trunk cables from the lines served terminate on a main distribution frame (MDF) at which they are connected to such devices as line protectors. There is also an intermediate distribution frame (IDF) to which are connected the switching and other equipments of the exchange. Connections between the two frames uses a pre-wired cable harness, so that the whole arrangement can be assembled and tested at the factory.