Communications: electrical – Selective – Having indication or alarm
Patent
1977-06-09
1980-01-22
Caldwell, Sr., John W.
Communications: electrical
Selective
Having indication or alarm
324226, 324261, 404 9, G08G 109, E01F 1100
Patent
active
041852656
ABSTRACT:
Coded binary signals are coupled to an automotive vehicle by a magnetic signpost embedded in a traversed roadway lane. The signpost includes polarity coded magnetic pole faces having vertically directed flux lines at differing spaced longitudinal regions along the lane. Pole faces are arranged so a flux null is between adjacent longitudinal regions. Differing signals are coupled to vehicles going in opposite directions in adjacent lanes by unambiguously coding the signpost in opposite directions and arranging the pole faces so that magnetic flux continuously extends across a majority of both lanes. A detector on a vehicle includes a magnetic field concentrator including a pair of vertically extending and aligned low reluctance magnetic pole pieces having an air gap between them, in which a Hall plate is positioned. The pole piece closest to the road has shorter length than the pole piece remote from the roadway. A waveform derived by the detector includes a base line subject to drift due to ambient conditions and a pulse as the transducer crosses each region. To eliminate base line drift, a circuit with a negative feedback loop derives an analog offset signal indicative of base line drift. Fail safe circuitry prevents spurious magnetic flux variations from being recognized as a signpost by assuring that a predetermined number of bits occurs in each signpost, and that the distance between the leading and trailing edges of the same pulse and the distance between adjacent pulses are in accordance with certain distances. Valid signals are derived if a vehicle stops or backs up while over a signpost.
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patent: 3493923 (1970-02-01), Stevens et al.
patent: 3609678 (1971-09-01), Fayling
patent: 3656059 (1972-04-01), Overstreet
patent: 3665382 (1972-05-01), Siklos
patent: 3714625 (1973-01-01), Fayling
patent: 3753223 (1973-08-01), Fayling
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patent: 3868626 (1975-02-01), Masher
patent: 3976970 (1976-08-01), Tuffet et al.
Griffin Noel J.
Knochelmann, Jr. Carl E.
Miller Larry D.
Squire Gerald K.
Caldwell Sr. John W.
Cincinnati Electronics Corporation
Groody James J.
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