Railway signal system with speed determined movement detector

Claim 2

A railway signal system for producing an output signal indicative of a train on a track approaching the system tie points to the track, comprising: means for generating an AC signal, said means for generating including means for coupling the same to said track, whereby said AC signal is transmitted in said track; means for automatically regulating the current level of said AC signal; in accordance with variations in the track ballast; and receiver means coupled to said track for receiving said AC signal from said track, said receiver means including means for detecting said AC signal to effect production of said system output signal in response to changes in said AC signal occurring due to such an approaching train.

Claim 3

The system of claim 1, further comprising electromechanical filter means coupled to said means for coupling and tuned to the frequency of said AC signal for providing an input signal to said means for automatically regulating, said input signal being proportionally representative of said AC signal generated by said means for generating and transmitted in said track.

Claim 4

A system as set forth in claim 2, further comprising an amplifier coupled to said electro-mechanical filter means; and an output circuit portion including an astable multivibrator having at least a first power input coupled to said receiver means; whereby when said astable multivibrator receives power, it is free running and when it does not receive power, it is not free running and said system output signal indicative of an approaching train is produced; and said amplifier being coupled to said output circuit portion to control production of said system outPut signal.

Claim 5

The system of claim 3, said output circuit portion comprising an output AC amplifier coupled to receive an input from said astable multivibrator, said first-mentioned amplifier being coupled to provide a power input to said output AC amplifier, whereby elimination of the first-mentioned amplifier output signal disables said output AC amplifier and said system output signal is then produced.

Claim 6

The system of claim 3, said astable multivibrator having a second power input coupled to said amplifier; whereby when both power inputs of said astable multivibrator receive power, said multivibrator is free running, and when at least one of said power inputs does not receive power, said multivibrator is not free running and system output signal indicative of an approaching train is produced.

Claim 7

The system of claim 1, said means for automatically regulating comprising an automatic gain control responsive to the average current level of said AC signal generated by said means for generating.

Claim 8

The system of claim 6, said means for generating comprising plural amplifier stages, the output from one stage being coupled to provide an input signal to the next stage, and an output of said automatic gain control being coupled to said amplfier stages for controlling the magnitude of input signal from said one amplifier stage to said next amplifier stage.

Claim 9

The system of claim 6, said automatic gain control including an electro-mechanical filter tuned to the frequency of said AC signal, said electro-mechanical filter being coupled to said means for coupling and hence providing an input signal to said automatic gain control in response to said AC signal.

Claim 10

The system of claim 6, said means for generating including an amplifier, and said automatic gain control being coupled to said amplifier to control the effective gain of said amplifier.

Claim 11

The system of claim 1, said means for generating comprising means for generating an AC carrier wave signal and means for periodically modulating said AC carrier wave signal, whereby said AC signal transmitted in said track by said means for generating is a modulated carrier wave signal; and further comprising means for controlling the sensitivity of said system comprising means responsive to the magnitude of said AC signal received at said receiver means from said track for adjusting the percent modulation of said AC carrier wave signal, thereby varying the effective power of said AC signal transmitted in said track by said means for generating.

Claim 12

The system of claim 10, said receiver means including a bridge rectifier for developing a DC signal proportionally representative of the voltage level of said AC signal received at said receiver from said track; and said means for adjusting comprising a transistorized circuit responsive to said DC signal for varying the percent modulation of said carrier wave signal.

Claim 13

The system of claim 1, said AC signal transmitted in said track comprising a track signal, and said means for generating normally generating said AC signal such that the voltage level of said track signal upon receipt at said receiver means is within a predetermined range; said system further comprising means for sensing when said track signal voltage level is outside said range, said means for sensing being coupled in said receiver means to effect production of said system output signal indicative of an approaching train upon such detection.

Claim 14

The system of claim 12, said means for sensing comprising high signal detector means for sensing received track signal voltage levels above said range and low signal detector means for sensing received track signal voltage levels below said range, and means for disabling said low signal detector means upon occurrence of a train leaving the system tie points to the track.

Claim 15

A railway signal system for producing an output signal indicative of a train on a track approaching the system tie points to the track, compriSing: means for transmitting a track signal in said track, said means for transmitting including means for generating an AC carrier wave signal, means for periodically modulating said carrier wave signal, and means for coupling said means for generating to said track, whereby said track signal comprises a modulated carrier wave signal; receiver means coupled to said track for receiving said track signal, said receiver means including means responsive to said track signal for producing said system output signal in response to changes in said track signal occurring due to an approaching train; and means responsive to the magnitude of said track signal received at said receiver means for automatically varying the sensitivity of said railway signal system, said means for varying comprising means for controlling the percent modulation of said carrier wave signal in response to the magnitude of said received track signal, thereby adjusting the effective power level of the track signal transmitted in said track.

Claim 16

A railway signal system for producing an output signal indicative of a train on a track approaching the system tie points to the track, compriSing: means for transmitting a track signal in said track, said means for transmitting including means for generating an AC carrier wave signal, means for periodically modulating said carrier wave signal, and means for coupling said means for generating to said track, whereby said track signal comprises a modulated carrier wave signal; receiver means coupled to said track for receiving said track signal, said receiver means including means responsive to said track signal for producing said system output signal in response to changes in said track signal occurring due to an approaching train; and means responsive to the magnitude of said track signal received at said receiver means for automatically varying the sensitivity of said railway signal system, said means for varying comprising means for controlling the percent modulation of said carrier wave signal in response to the magnitude of said received track signal, thereby adjusting the effective power level of the track signal transmitted in said track.

Claim 17

The system of claim 14, said receiver means comprising a bridge rectifier for producing a DC signal proportionally representative of the voltage level of said track signal received by said receiver means from said track; said means for controlling comprising a first transistorized circuit responsive to said DC signal, and a second transistorized circuit responsive to said first transistorized circuit for contolling the percent modulation of said AC carrier wave signal.

Claim 18

The system of claim 15, further comprising means for manually controlling conduction in said second transistorized circuit.

Claim 19

The system of claim 16, said means for generating an AC carrier wave signal comprises a tone generator and said means for periodically modulating comprises a unijunction transistor and capacitor oscillator for developing modulating pulses to modulate said AC carrier wave signal, said second transistorized circuit being coupled between said tone generator and oscillator for controlling the size of said modulating pulses.

Claim 20

A railway signal system for producing an output signal indicative of a train on a track approaching the system tie points to the track, comprising: means for generating an AC signal, said means for generating including means for coupling the same to said track, whereby said AC signal is transmitted in said track; means for monitoring the current level of said AC signal generated by said means for generating and transmitted in said track, said means for monitoring including an electromechanical filter tuned to the frequency of said AC signal, and said means for monitoring producing an output signal indicative of the current level of said AC signal generated by said means for generating and transmitted in said track; receiver means coupled to said track for receiving said AC signal from said track, said receiver means including means for detecting said AC signal, said means for detecting providing an AC output indicative of such detection; and an output circuit portion means being coupled to said receiver means and to said means for monitoring for developing said system output signal indicative of an approaching train when said AC signal is not detected at said means for detecting or the current level of said AC signal falls below a predetermined minimum level.

Claim 21

A railway signal system for producing an output signal indicative of a train on a track approaching the system tie points to the track, comprising: means for generating an AC signal, said means for generating including means for coupling the same to said track, whereby said AC signal is transmitted in said track; means for monitoring the current level of said AC signal generated by said means for generating and transmitted in said track, said means for monitoring including an electromechanical filter tuned to the frequency of said AC signal, and said means for monitoring producing an output signal indicative of the current level of said AC signal generated by said means for generating and transmitted in said track; receiver means coupled to said track for receiving said AC signal from said track, said receiver means including means for detecting said AC signal, said means for detecting providing an AC output indicative of such detection; and an output circuit portion means being coupled to said receiver means and to said means for monitoring for developing said system output signal indicative of an approaching train when said AC signal is not detected at said means for detecting or the current level of said AC signal falls below a predetermined minimum level.

Claim 22

The system of claim 18, said output circuit portion means comprising an astable multivibrator having first and second power input circuits, said first input circuit being coupled to said means for detecting and said second input circuit being coupled to said means for monitoring.

Claim 23

The system of claim 18, said output circuit portion means comprising an amplifier having at least one power input, said means for monitoring being coupled to said at least one power input, whereby when the power level of said AC signal falls below a predetermined level said amplifier is disabled and said system output signal indicatIve of an approaching train is produced.

Claim 24

A railway signal system for producing an output signal indicative of a train on a track approaching the system tie points to the track, comprising: means for transmitting a track signal in said track, said means for transmitting including means for generating an AC signal and means for coupling said means for generating to said track; receiver means coupled to said track for receiving said track signal, said receiver means including an output circuit portion means for developing said system output signal upon occurrence of an approaching train; said means for generating normally generating said AC signal such that the voltage level of said track signal upon receipt at said receiver means is within a predetermined range; and means for sensing when such voltage level is outside said range, said means for sensing being coupled in said receiver means to effect production of said system output signal indicative of such an approaching train when such voltage level is outside said range.

Claim 25

A railway signal system for producing an output signal indicative of a train on a track approaching the system tie points to the track, comprising: means for transmitting a track signal in said track, said means for transmitting including means for generating an AC signal and means for coupling said means for generating to said track; receiver means coupled to said track for receiving said track signal, said receiver means including an output circuit portion means for developing said system output signal upon occurrence of an approaching train; said means for generating normally generating said AC signal such that the voltage level of said track signal upon receipt at said receiver means is within a predetermined range; and means for sensing when such voltage level is outside said range, said means for sensing being coupled in said receiver means to effect production of said system output signal indicative of such an approaching train when such voltage level is outside said range.

Claim 26

The system of claim 21, said means for sensing comprising high signal detector means for sensing voltage levels above said range and low signal detector means for sensing voltage levels below said range, and means for disabling said low signal detector means upon occurrence of a train leaving the system tie points to the track.

Claim 27

The system of claim 22, said means for sensing comprising a transistorized output circuit coupled to said receiver output circuit portion means for effecting production of said system output signal upon energization of said transistorized output circuit.

Claim 28

The system of claim 23, wherein said low signal detector means comprises a first transistorized circuit normally energized when such voltage level is within said range to maintain de-energization of said transistorized output circuit, and said high signal detector means comprises a second transistorized circuit normally de-energized when such voltage level is within said range, said second transistorized circuit being coupled to said first transistorized circuit, whereby when such voltage level is above said range said second transistorized circuit is energized to effect de-energization of said first transistorized circuit and energization of said transistorized output circuit.

Claim 29

The system of claim 24, said means for disabling comprising an SCR coupled between the output of said first transistorized circuit and the input from the latter to said transistorized output circuit, means for energizing said SCR upon detection of an approaching train thereby eliminating energization of said transistorized output circuit, means for precluding energization of said SCR when no train is detected, and timer circuit means for assuring continued conduction in said SCR for a time period upon occurrence of a leaving train.

Claim 30

The system of claim 25, said receiver means comprising a motion detection portion normally producing an AC output upon receipt by said receiver means of said track signal when no train has been detected, said AC signal normally being coupled to said disabling circuit.

Claim 31

The system of claim 21, further comprising means for monitoring said AC signal generated by said means for generating, an output from said means for monitoring being coupled to said receiver means output circuit portion means for controlling the same such that when the power level of said AC signal falls below a predetermined level said output circuit portion means is controlled to develop said system output signal indicative of an approaching train.

Claim 32

The system of claim 27, said means for sensing comprising high signal detector means for sensing such voltage levels above said range, said high signal detector means being coupled to said means for monitoring to disable the same, whereby upon occurrence of such voltage level above said range said high signal detector disables said means for monitoring effecting control of said output circuit portion means to develop said system output signal indicative of an approaching train.

Claim 33

The system of claim 28, said receiver means comprising means for producing a DC signal proportionally representative of said track signal voltage level, said high signal detector means comprising a resistance divider circuit, and said means for monitoring comprising an AC amplifier, whereby upon occurrence of a track signal voltage level above said range, said high signal detector biases said AC amplifier to saturation so that no output signal is produced by the latter.

Claim 34

The system of claim 28, said means for sensing further comprising low signal detector means for producing a first output signal when said track signal voltage level is within said range and a second output signal when said track signal voltage level is below said range, said low signal detector means being coupled to said receiver means output circuit portion means such that application of said second output signal to said receiver means output circuit portion means causes the latter to develop said system output signal indicative of an approaching train, and further comprising means coupled to said receiver means for disabling said low signal detector means upon occurrence of a leaving train.