Impromptu is a mobile audio device which uses wireless Internet Protocol (IP) to access novel computer-mediated voice communication channels. These channels show the richness of IP-based communication as compared to conventional mobile telephony, adding audio processing and storage in the network, and flexible, user-centered call control protocols. These channels may be synchronous, asynchronous, or eventtriggered, or even change modes as a function of other user activity. The demands of these modes plus the need to navigate with an entirely non-visual user interface are met with a number of audio-oriented user interaction techniques.

Hydrophobicity of polymeric insulators is one of the main properties that determine their performance in polluted environments. The hydrophobic property is reduced as the insulator's surface ages due to the electric activity caused by wetting and pollution; however, it is recovered during the resting time in air. The insulators having a high rate of hydrophobicity recovery show better performance.Polymeric insulators of different materials and leakage distances were evaluated in laboratory by using an accelerated ageing method. The hydrophobic property of each insulator was studied by measuring the contact angle on the insulator's surface where the highest electric activity was observed. The measurements were performed before and several times along the ageing test. The performance of the insulators was evaluated by the number and magnitude of the peaks of leakage-current recorded by a home-made system during the entire test. The results show than if the hydrophobic property of the insulator's surface is low, the performance of the insulator under wet and polluted conditions may be strongly affected by its leakage distance.

Impromptu is a mobile audio device which uses wireless Internet Protocol (IP) to access novel computer-mediated voice communication channels. These channels show the richness of IP-based communication as compared to conventional mobile telephony, adding audio processing and storage in the network, and flexible, user-centered call control protocols. These channels may be synchronous, asynchronous, or eventtriggered, or even change modes as a function of other user activity. The demands of these modes plus the need to navigate with an entirely non-visual user interface are met with a number of audio-oriented user interaction techniques.