Abstract: A multichannel data compressor (20) for a data transmission system having a plurality of data sources. The multichannel data compressor has a plurality of data latches (44,46,48) for temporarily storing the data generated by each data source and a plurality of difference circuits (52,54,56), one for each data source, which subtract the data stored in the data latches from the next subsequent data value generated by the data sources to generate a difference data value. A plurality of summing circuits (58,60,62) sum the difference data values to generate a plurality of composite data values. A selector switch (64) transfers the composite data values or selected current data values to a multiplexer (72) when the magnitude of at least one of the composite data values exceeds a predetermined value. The multiplexer (72) formats the received data into a predetermined format, converts it to a serial format, then forwards the data to a transmitter for transmission.