Phase selective track circuit apparatus

Details Phase selective track circuit apparatus Phase selective track circuit apparatus

1975-05-30

1976-10-19

Kunin, Stephen G.

Railway switches and signals

Block-signal systems

Automatic

333 76, 333 77, B61L 2316

Patent

active

039866912

ABSTRACT:
A frequency selective filter is connected between the track transformer and phase selective unit at the receiving end of a coded phase selective track circuit to reject interfering signals of propulsion current frequency. The series L-C filter comprises a capacitor and a two-winding reactor coil with a resistor permanently connected in series between the two windings. Each winding is tapped to allow a selection of the filter inductance to match track circuit impedance, including impedance bonds and ballast resistance. Taps for short track circuits include the second winding and the resistor to improve signal to noise ratio. Energy for short interlocking track circuits is of a higher frequency, and a special tap on the first winding is selected to enable filter tuning at this other frequency for train detection since basic frequency is still used during code off-time for cab signal control.

REFERENCES:
patent: 2310797 (1943-02-01), Lea
patent: 2709788 (1955-05-01), Schmidt, Jr.
patent: 3475702 (1969-10-01), Ainsworth
patent: 3524054 (1970-08-01), Smith
patent: 3781540 (1973-12-01), Staples
patent: 3821544 (1974-06-01), Matty

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