People faced with an unfamiliar product or service tend to fall back on mental models based on analogical relationships with familiar products or services. Two experiments on the analogical relationships or metaphors that people might use when operating a communications terminal are described. In the first experiment, the role previously acquired operating knowledge has in determining the mental models people use when directory dialing with novel equipment is examined. In a second experiment, it is shown that an explicit appeal to an analogy between conventional mail and electronic mail can help users learn to use an electronic mail system, and make it easier for them to remember how to use the system as long as 90 days after initial exposure. It is concluded that the mental model is constructed only from the user's operating knowledge acquired as a result of past experiences, and the metaphor method is effective when the instructions are metaphorically taught.>

A sample-interpolation method based on pattern matching is proposed to reduce speech quality degradation caused by packet losses. This method is used together with packet interleaving, which simplifies the recovery of missing packets to the recovery of missing sample values. The interpolation method is evaluated by an opinion test. The results show that speech quality is satisfactory up to a packet loss rate of 5% when packets are discarded randomly. It is satisfactory up to a packet loss rate of 10% when packet discarding is controlled to prevent consecutive packet losses.>