Abstract:
The apparatus has a probe (13) for collecting a small portion of a carrier signal on a pair of wires (37). The collected portion of the carrier signal is mixed with a local oscillator (17) signal so as to produce a heterodyned signal having a low frequency component and a high frequency component. The frequency of the local oscillator signal is selected to be within a few Kilohertz of the carrier signal so that the low frequency component is within an audible range. A low pass filter (19) removes the high frequency component. The low frequency component is amplified (21) and converted to sound. The audible signal is a representation of the carrier signal and allows a technician to determine the relative strength of the carrier signal and to identify the type of carrier signal on the wire pair.
Abstract:
A passive marker (9) is placed adjacent to a structure (58) in order to locate that structure after burial. The marker has a tuned circuit arrangement (29) contained within a housing (31). The tuned circuit arrangement has plural tuned circuits (11, 17, 23) that are oriented substantially orthogonally to each other. A multidirectional response pattern (19) is produced by the tuned circuit arrangement, which pattern is broader than the directional response pattern (15) of a single tuned circuit. The housing is divided into two hemispheres (39, 41) for ease of assembly. Each hemisphere has channels (45, 57, 49) formed therein for receiving the respective tuned circuits. The channels can be formed by the exterior wall of the housing, interior walls (67) of the housing, or in an interior spherical mandrel (87).
Abstract:
The apparatus of the present invention includes an audio encoder (19) and decoder (21), a memory (27), a transmitter (38) and a receiver (40) that are optically coupled to an optical fiber (17), and a controller (23). The audio encoder (19) produces samples of an audio input at a regular rate. The samples are accumulated in the memory (27). When enough samples have been accumulated, the transmitter (38) begins to transmit the accumulated samples over the optical fiber (17) in a burst. After transmitting, the apparatus pauses long enough to allow reflections on the optical fiber (17) to attenuate to an undetectable level. Then, the receiver (40) is actuated to receive any incoming burst of data, wich are stored in memory (27) until sent to the audio decoder (21).