Railway switches and signals – Block-signal systems – Automatic
Patent
1985-07-16
1988-02-09
Caldwell, Sr., John W.
Railway switches and signals
Block-signal systems
Automatic
246 34CT, 246 63C, 246 34R, B61L 100
Patent
active
047237392
ABSTRACT:
An improved audio frequency track circuit system utilizes a synchronous train detection arrangement and reduces the number of fixed code rate modulated carrier signals. As few as two carrier signals are alternately applied at discrete points along a pair of jointless track rails to define the transmitter ends of the track sections, with complementary receivers defining the opposite ends. The two carrier signals are coded at one of two phase angles which are 90.degree. out-of-phase so that, when assigned, the nearest possible interfering signal is 90.degree. out-of-phase and is rejected thereby. Like carrier frequency transmitter/receiver arrangements are disposed on opposite sides of an insulated joint but are coded 180.degree. out-of-phase so that a breakdown of the insulated joint is detected and the false code signal is rejected.
REFERENCES:
patent: 3526378 (1970-09-01), Thorne-Booth
patent: 3970271 (1976-07-01), Auer et al.
patent: 3974991 (1976-08-01), Geiger
patent: 4065081 (1977-12-01), Huffman et al.
patent: 4304377 (1981-12-01), Pitard
patent: 4306694 (1981-12-01), Kuhn
patent: 4314306 (1982-02-01), Darrow
patent: 4535959 (1985-08-01), Gilcher
American Standard Inc.
Caldwell Sr. John W.
Oberley Alvin
Sotak J. B.
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