least one network interface unit niu 20 at least one bridge processing unit bpu 22 and a host processing unit hpu 24 in addition there can be optional audio processing units apus 28 each of these components is a digital device for processing digital data in addition to a host industry standard architecture isa bus 32 the mcu 10 includes a network bus 34 and a bpu bus 36 the network bus 34 complies with the multi vendor integration protocol mvip while the bpu bus 36 is a derivative of the mvip specification external audiovisual terminals or codecs 38 connect to the mcu 10 to form conferences the mcu operation will now be described at a high level with respect to fig2 each codec 38 typically an h 320 audiovisual terminal connects to the mcu 10 through a communications network unsynchronized digital data frames from each codec 38 are made available on the network bus 34 through nius 20 the bpus 22 process the unsynchronized data frames from the network bus 34 to produce data frames aligned on an octet boundary which are made available to other bpus 22 on the bpu bus 36 the bpus 22 also extract audio information from the data frames the audio information is decoded to pcm data and made available on the bpu bus 36 for mixing with audio from other codecs 38 by respective bpus 22 in a conference the bpus 22 combine compressed video information and mixed encoded audio information into frames which are placed on the network bus 34 for transmission to.