Lightning surges induced on subscriber lines in Kuala Lumpur, Malaysia, which is located in a tropical region, were observed at telecommunication centers. More than 100 surges per line were observed during a three-month period. Peak values, observed using a lightning surge counter, show that lightning surge current occurrences normalized by the number of thunderstorm days and number of subscriber lines closely agreed with data observed in temperate areas, e.g., Japan. Surge waveforms appearing at several points ranging from underground cable ducts to exchange equipment were observed using a wave memory system. The results show that lightning surge currents on the cables were larger than those on a wire, but the correlation between them was weak. Common and differential mode surge waveforms observed using the wave memory system were almost the same. These results will be useful in designing protection circuits for equipment used in tropical areas.

A method of predicting disturbances to TV signal reception has been developed in order to workout countermeasures for interference caused by unwanted emissions from information technology equipment (ITE). The prediction parameters were determined by measuring the emission levels from ITE at an open test site, propagation characteristics of unwanted emissions from ITE in a building, the output power of the TV transmitting station, the propagation characteristics of the TV radio waves, and the directivity of the TV receiving antenna. The possibility of disturbances occurring in the Kanto area was predicted and the results show that, in the worst case, a disturbance will appear in about 11% of the areas within 30 m of a building containing such equipment. This also shows that the disturbance can be suppressed by improving the shielding of the equipment or building by as little as 10 dB.