Currently, LAMA(Local Automatic Message Accounting) is a billing mechanism which is being used for billing process, in which billing dat is written on MT(Magnetic Tape), collected at each regional billing center and then processed once a month. However, in order to prepare further development of telecommunication network and future new services, computerization of billing process and new daily billing processing system are urgently needed. Therefore Korea Telecom had developed a CAMA (Centralized Automatic Message Accounting) system for M10CN switch. In the CAMA system, billing data generated in switches is transfered on-line using approproate protocols and various transmission media and immediately processed. The CAMA system for M10CN switch consists of three parts such as ED (Extraction Device), TD(Transmission Device) and HC(Host Collector). The system also has redundancy to maintain continuance and confidence of system operation.