05043950 is referenced by 21 patents and cites 9 patents.

The disclosure is directed to an apparatus and method for determining the travel time of acoustic energy over an unknown travel distance between an acoustic transmitter and an acoustic receiver. This information can be used, for example, to determine the position of a moveable element in a data space. A timer is initiated at the time of acoustic transmission from the transmitter. A control signal generator is provided, and is initiated at the time of acoustic transmission from the transmitter, the control signal being a function of the time which elapses after the time of acoustic transmission. The gain of the signal received at the receiver is controlled in accordance with the control signal. The timer is terminated when the gain-controlled received signal exceeds a predetermined threshold. In a preferred embodiment, the terminating means includes a comparator for comparing the gain-controlled received signal to the predetermined threshold. The magnitude of the control signal varies as

Title
Apparatus and method for distance determination
Application Number
7/467662
Publication Number
5043950
Application Date
January 19, 1990
Publication Date
August 27, 1991
Inventor
Robert Butler
Milford
CT, US
Stanley Schorum
Madison
CT, US
Agent
Martin Novack
Assignee
Science Accessories
CT, US
IPC
G08C 21/00
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