Abstract: The disclosure is directed to a circuit for producing electrical discharges in response to trigger signals, and a form of the disclosure is directed to an apparatus, which includes such a circuit, for determining the transit time of acoustic energy travel between a transmitter location and a receiver location.

Abstract: The disclosure is directed to a method and apparatus for more accurately determining the transit time of acoustic energy travel between a transmitter location and a receiver location. An electrode pair spark gap is provided at the transmitter location, and an acoustic receiver is provided at the receiver location. The spark-gap is energized to produce a spark by coupling an electrical potential across the electrode pair. The generation of a spark at the spark gap is sensed, and an initializing signal is generated in response thereto. A timer is initialized in response to the initializing signal. The receipt of acoustic energy from the spark is detected at the receiver location and a terminating signal is generated in response thereto. The timer is terminated in response to the terminating signal, and the time measured by the timer is indicative of the transit time of acoustic energy travel between the transmitter and receiver locations.

Abstract: 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.