OSCILOSCOPES SPECTROANALYZERS AND OTHER INSTRUMENTS AND APPARATUS FOR MEASURING OR CONTROLLING ELECTRICAL QUANTITIES OTHER THAN MEASURING INSTRUMENTS OF HEADING 9028; INSTRUMENTS AND APPARATUS FOR THE DETECTION OR MEASUREMENT OF ALPHA BETA GAMMA X-RAY COSMIC AND OTHER IONIZING RADIATION: - OTHER INSTRUMENTS AND APPARATUS SPECIALLY INTENDED FOR TELECOMMUNICATIONS (FOR EXAMPLE CROSS INTERFERENCE DETECTORS AMPLIFICATION COEFFICIENTS CURVATURE COEFFICIENTS PSOPHOMETERS)