Resistive Plate Chamber (RPC) based muon trigger system for the CMS experiment – data compression/decompression system

The CMS detector will have a dedicated subdetector (RPC chambers) to identify muons, measure their transverse momenta pt, and determine the bunch crossings from which they originate. The trigger algorithm is based on muon track search and classification in raw data from the RPC chambers grouped in the four muon stations in the CMS magnet yoke. A huge interconnection network is needed to fulfill this task. It can be built in the control room only, approximately 120 m away from the detector. The data compression/decompression system is proposed to reduce the number of links needed to transfer the data from detector to control room. The idea of such a system and results of first tests will be presented.