An apparatus for detecting and timing a transmitting device is disclosed. The device includes a receiving system receiving a signal containing at least a preamble code of a known length and at least one pulse within a receive window after the preamble code, a circuit receiving the at least one pulse comprising a zero-crossing circuit for indicting a zero-voltage crossing of the at least one pulse and a trigger device for latching the indication of zero-voltage crossing, and a ripple circuit counter, receiving the latched indication of said zero-voltage crossing and associating a time to the receipt of the latched indication. A system for detecting and locating a transmitting device is further disclosed. The system includes a plurality of sensor apparatus each determining a reception time of a signal and a processor for determining a location based on groups of the reception times