Its transmitter assembly that was surrounded by a hollow enclosure known colloquially as a " spit cup ", which would focus sound more effectively into the transmitter.
2.
Smaller-scale inflatables ( such as pool toys ) generally consist of one or more " air chambers ", which are hollow enclosures bound by a soft and flexible airtight material ( such as vinyl ), which a gas can enter into or leave from through valves ( usually one on each air chamber ).
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