Abstract: A bit-sampling multiplexer apparatus includes two terminals, each having a transmitter portion and a receiver portion. A transmitter in one terminal multiplexes data on a plurality of incoming data channels into a serial data frame, and couples this frame across a high-speed digital data communication line to the opposite terminal. The communication line comprises a physical twisted pair cable, optical fiber, or other suitable means for transporting digital data. Two separate lines are provided to enable communication in both directions between said terminals. The transmitter portion of each terminal periodically samples each of a plurality of data channels connected thereto at a rate significantly faster than the bit rate of each such channel, to generate the serial data frame. Each transmitter may also include an edge detector for generating a signal when a state change is detected in one or more high priority data channels.