On-premises emission testing of digital switching systems

A procedure that has been successfully used for on-premises testing of telephone switching systems with time-division networks is described. Procedures and special test equipment that have been developed during the past seven years while testing nearly 30 different sites are described. Tools for separating equipment-under-test (EUT) emissions from ambient emissions include a customized, frequency-comb generator that simulates signals from the EUT. Compliance determination using on-premises testing has proved both practical and feasible. The procedure is also useful for identifying major emission sources and possible areas of equipment improvement