Abstract: The invention relates to a multiplexer, a demultiplexer and to multiplexing-demultiplexing equipment with configurable frames.The reconfigurable frame multiplexer comprises a synchronous multiplexer, means for inserting a frame locking word, transmission management means, monitoring means and a microprocessor for controlling or communicating with the aforementioned means. A time base emits timing and synchronization signal for emitting a frame. This time base comprises a memory containing data, which codes the present frame configuration. During the reading of this memory by a fast time base, another memory is filled by the microprocessor in order to code a new frame configuration.