Traffic control system
First Claim
1. A traffic control system comprising:
- (A) a transmitter unit including;
(1) circuit means for transmitting a carrier signal(2) circuit means for selectively modulating the carrier signal with a first modulation signal at a first frequency, and(3) circuit means for selectively modulating the carrier signal with a second modulation signal at a second frequency different from the first frequency, and(B) a receiver unit for receiving the transmitted carrier signal and any modulation thereof by said first and second modulation signals and adapted to produce in response to receipt of the carrier signal modulated by both modulation signals and in cyclic sequence display of green, amber and red visual traffic signals, the receiver including;
(1) a first detector detecting the said first modulation signal and producing a corresponding first control signal,(2) a second detector detecting the said second modulation signal and producing a corresponding second control signal, and(3) receiver circuit means requiring receipt of both said first and second control signals, for longer than a predetermined period and responsive to such receipt to cause display of the green visual traffic signal,(C) wherein the transmitter includes circuit means for generating a pulse of the said carrier modulated by said first and second modulation signals, which pulse is of a period shorter than the said predetermined period required for the said display of the green visual signal, andwherein the receiver circuit means is responsive to receipt of both said first and second control signals for a period longer than the said pulse to cause the said display of the green visual signal, is responsive to cessation of receipt of at least one of said control signals to cause display of the amber visual signal, and is responsive to receipt of the said pulse to cause display of the amber visual signal without prior display of the green visual signal.
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Accused Products
Abstract
In a portable traffic control system in which receivers are controlled from a central transmitter the carrier signal employed is modulated by two different modulation signals in order to command a green light to be shown, reducing the possibility of this happening accidentally. The receipt of a carrier signal with only a single pilot modulation causes production of a red signal. An amber caution light if present is lit automatically upon turning off green, and flashing amber is produced by switching on green and then turning it off before the green can be lit. A drop in battery voltage below a predetermined level will cause a flashing red signal to warn and conserve the battery power. A non-resettable link in circuit with the green light is broken upon existence of a malfunction condition whereby another light is lit while green is alight, so that the green can no longer be lit until the unit is serviced to remove the malfunction.
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Citations
24 Claims
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1. A traffic control system comprising:
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(A) a transmitter unit including; (1) circuit means for transmitting a carrier signal (2) circuit means for selectively modulating the carrier signal with a first modulation signal at a first frequency, and (3) circuit means for selectively modulating the carrier signal with a second modulation signal at a second frequency different from the first frequency, and (B) a receiver unit for receiving the transmitted carrier signal and any modulation thereof by said first and second modulation signals and adapted to produce in response to receipt of the carrier signal modulated by both modulation signals and in cyclic sequence display of green, amber and red visual traffic signals, the receiver including; (1) a first detector detecting the said first modulation signal and producing a corresponding first control signal, (2) a second detector detecting the said second modulation signal and producing a corresponding second control signal, and (3) receiver circuit means requiring receipt of both said first and second control signals, for longer than a predetermined period and responsive to such receipt to cause display of the green visual traffic signal, (C) wherein the transmitter includes circuit means for generating a pulse of the said carrier modulated by said first and second modulation signals, which pulse is of a period shorter than the said predetermined period required for the said display of the green visual signal, and wherein the receiver circuit means is responsive to receipt of both said first and second control signals for a period longer than the said pulse to cause the said display of the green visual signal, is responsive to cessation of receipt of at least one of said control signals to cause display of the amber visual signal, and is responsive to receipt of the said pulse to cause display of the amber visual signal without prior display of the green visual signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A traffic control system comprising:
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(A) a transmitter transmitting a control signal for control in a receiver of the display by the receiver in cyclic sequence of green, amber and red visual traffic signals, and (B) at least one said receiver receiving the said control signal and responsive thereto to cause the said dispaly; (C) the transmitter including circuit means for generating and transmitting a green form of said control signal adapted to cause display by each said receiver receiving the said green form control signal of said green visual signal, and for generating and transmitting a pulse of said green form of the control signal of period considerably shorter than that required for said cyclic display of the green visual signal; (D) each said receiver including circuit means responsive to receipt of said green form of the control signal for a period longer than the said pulse to cause the said cyclic display of the green visual signal, responsive to cessation of said green form of the control signal to cause display of the amber visual signal, and responsive to receipt of said pulse to cause display of the amber visual signal without prior display of the green visual signal. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification