Railway switches and signals – Block-signal systems – Automatic
Patent
1980-05-23
1982-10-05
Groody, James J.
Railway switches and signals
Block-signal systems
Automatic
246 34R, 246 63C, 246121, 246167R, B61L 2100, B61L 300
Patent
active
043524753
ABSTRACT:
An audio frequency track circuit with improved security in the train detection function for rapid transit applications for use with uninsulated rails includes an improved transmitter and receiver. The transmitter modulates a track frequency carrier with a fixed code rate, regardless of the code rate employed to modulate the train information frequency. The receiver includes a decoder tuned to the track frequency modulation rate. By using such a sharply tuned decoder, the noise protection threshold is increased. Because of its application to uninsulated rails, with the associated lack of hard track circuit boundaries, adjacent track circuits have different track frequency modulation rates to insure that the modulated track frequency signal, from one track circuit, is not effective to operate a track relay in another circuit even under failure conditions.
REFERENCES:
patent: 3361905 (1968-01-01), Baughman
patent: 3450875 (1969-06-01), Whitten et al.
patent: 3794833 (1974-02-01), Blazek et al.
patent: 3868075 (1975-02-01), Blazek et al.
patent: 3946972 (1976-03-01), Grundy
patent: 4065081 (1977-12-01), Huffman et al.
patent: 4074879 (1978-02-01), Clark et al.
Hoelscher James R.
Smith Barry L.
General Signal Corp.
Groody James J.
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