RECEIVER FOR A FREQUENCY MODULATED OVERLAY TRACK CIRCUIT

• US 3,715,669 A
• Filed: 08/13/1970
• Issued: 02/06/1973
• Est. Priority Date: 08/13/1970
• Status: Expired due to Term

• Current Assignee: John P. Laforest
• Original Assignee: John P. Laforest
• Inventors: LaForest, John P.
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Martin, John C.
• Application Number:
  US05/063,453
• Time in Patent Office: 908 Days
• Field of Search: 246/34R,34B,34CT,40,128-130 325/30,320,344 178/66 340/49,258C,38
• US Class Current: 375/334
• CPC Class Codes: B61L 1/188 Use of coded current
• CPC Class Codes: H01H 47/002 Monitoring or fail-safe circuits
• CPC Class Codes: H01H 47/20 for producing frequency-selective operation of the relay

Abstract

A receiver is provided for a frequency modulated overlay track circuit in which a frequency modulated signal having alternately occurring extreme side-band components is communicated along a railroad right of way. The system which is subject to the influence of the presence of a railroad vehicle comprises, a tuner means responsive to the F.M. signals separating one sideband component of the signal from the other and polarizing means for generating distinctive signals of opposite polarity in response to the respective side-band components. A relay is provided which is responsive to the distinctive signals occurring periodically and alternately for providing manifestation of a clear right of way.

Claims

1. A receiver in a frequency modulated overlay track circuit for communicating a frequency modulated signal having alternately occuring first and second frequency components, along a right of way subject to the influence of the presence of a vehicle comprising:

a. tuner means responsive to said F.M. signals for producing a first output signal which includes only said first frequency components and a second output signal which includes only said second frequency components;

b. polarizing means responsive to said first and second output signals for providing third and fourth output signals of opposite polarity respectively; and

c. means responsive to said third and fourth output signals for generating a continuous signal to manifest a clear right of way provided that said output signals for the respective components occur periodically in substantially a 180 phase relation one to the other.

2. The receiver of claim 1 wherein said polarizing means comprises:

a solid state unidirectional device coupled to each tuned circuit responsive to only one of said frequency components and conducting only upon the reception of a corresponding side-band signal.

3. The receiver of claim 2 wherein said solid state unidirectional device comprises:

one transistor each of opposite conductive types, conducting only upon occurrence of a correct current polarity input.

4. The receiver of claim 2 further including:

filtering means coupled to the outputs of the unidirectional devices responsive respectively to the associated frequency component for filtering out alternating current components of said outputs.

5. The receiver of claim 2 wherein said polarizing means further comprises:

first solid state switching means coupled to the output of each of said unidirectional devices for conducting in response to the conductance state of its associated device.

6. The receiver of claim 5 wherein said first switching means comprises:

a transistor of similar conductance type to its associated unidirectional device having its base coupled to the output of said device and conducting in accordance therewith.

7. The receiver of claim 6 wherein second solid state switching means is provided for each first switching means responsive to the outputs thereof and conducting in accordance therewith;

and storage means associated with each second switching means for storing energy each time said associated second switching means is non-conducting and discharging each time the other second switchiNg means is conductive.

8. The receiver of claim 7 wherein each one of said charging means receives storage energy each time its associated second switching means is closed and the other second switching means is open.

9. The receiver of claim 7 wherein said second switching means comprises:

a transistor for each associated first switching means of opposite conductance type than its associated first switching means.

10. The receiver of claim 7 wherein said charging means comprises:

a tank circuit coupled to the output of each of said second switching means including a resistor and capacitor; and

a diode for each tank circuit coupled for permitting charging of each of said tank circuits only when the associated second switching means is in a non-conductance state.

11. The receiver of claim 1 wherein an output relay means is provided having two inputs governed by outputs of the polarizing means either one of which when energized is capable of actuating said relay.

12. The receiver of claim 11 wherein said output relay is a magnetically biased polar relay having one input thereof only responsive to outputs of the polarizing means of one polarity and the other input responsive to outputs of the polarizing means of opposite polarity, said relay being actuated for closing its front contact only when said outputs occur periodically in a 180* phase relation one to the other.

13. The receiver of claim 12 wherein said relay is coupled between a supply source and the output of said polarizing means in opposite polarity to normal energizing current, and said outputs of the polarizing means having a potential relatively greater than the supply source for energizing the relay upon the occurrence of said periodic outputs of the polarizing means.

14. A receiver for a continuous frequency modulated signal having periodically alternate first and second side-band frequency components, the receiver having a tuner which provides said first side-band component at one output and said second side-band component at another output wherein the improvement comprises:

a. polarizing means responsive to the respective tuner outputs for generating output signals of opposite polarity respectively, and b. decoding means responsive to the signals of opposite polarity for delivering a continuous output signal only provided that the outputs of the polarizing means occur periodically and alternately.

15. A receiver according to claim 14 wherein the polarizing means comprises a capacitor and means for charging the capacitor in response to one of the tuner outputs and discharging the capacitor in response to the other of the tuner outputs.

16. A receiver according to claim 15 wherein the polarizing means comprises a second capacitor and means for charging the second capacitor in response to said another tuner output and discharging the second capacitor in response to said one tuner output.

17. A receiver according to claim 16 wherein the decoding means is governed by the discharge of the first and second capacitors to deliver an output only provided the capacitors are discharged periodically and alternately.