Abstract: A method of validating connection data for a node of a telephone network involves processing a report file for terminal pairs at a network node. The records in the report file are divided into three categories in dependence on the nature of the information in each record. A network status database is then updated with the report data category by category. Circuit IDs in the network status database that are deleted by updating in respect of records belonging to other then the last processed category are recorded against a record in the network status database corresponding to a record in the last processed category. Circuit IDs in the network status database that are deleted by updating in respect of last-processed category records are logged to provide a list of circuit IDs for which further investigation is required.

Abstract: A receiver circuit for receiving a modulated optical signal and for generating a corresponding electrical signal comprises a photodiode (1) for receiving the optical signal and for generating a first modulated electrical signal. An amplification circuit (3) receives the first electrical signal or a signal related thereto via an n stage (where n is an odd-integer) filter network (2) connected between the photodiode (1) and the amplification circuit (3). The output from the amplification circuit is fed to a first equalization amd noise filter (5). The characteristics of the filter network are such that the total thermal noise power output of the first noise filter is substantially minimized.