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# Vehicle Speed Signalling Device

IP.com Disclosure Number: IPCOM000094830D
Original Publication Date: 1965-Jun-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 29K

IBM

## Related People

Berger, JM: AUTHOR [+4]

## Abstract

This apparatus uses the Doppler effect to signal a driver when he is exceeding the speed limit. A sonic or ultrasonic radiator 10, beamed at the oncoming traffic, emits a tone signal which is a function of the speed limit and corrected for ambient conditions. The sonic signal is received by a forward pointing receiver 11 on each vehicle where it is beat against a fixed tone. The beat frequency is thus a function of the relativity of the vehicle speed to the speed limit.

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Vehicle Speed Signalling Device

This apparatus uses the Doppler effect to signal a driver when he is exceeding the speed limit. A sonic or ultrasonic radiator 10, beamed at the oncoming traffic, emits a tone signal which is a function of the speed limit and corrected for ambient conditions. The sonic signal is received by a forward pointing receiver 11 on each vehicle where it is beat against a fixed tone. The beat frequency is thus a function of the relativity of the vehicle speed to the speed limit.

If, for example, the speed limit is 30 m.p.h. (44 feet per second), the velocity of sound toward the vehicle is 1000 feet per second (corrected for wind, temperature, pressure and humidity), and the fixed frequency tone generator is 20,000 cycles per second, the frequency of the transmitted signal T equals 20,000 >(1000t44)/1000| = 19,120c.p.s.

Because of the Doppler effect, the transmitted tone is received at a frequency which is a function of the vehicle speed. If the vehicle is travelling at 60 feet per second (approximately 41 m. p. h.), then the received tonal frequency R equals 19, 120 (1000/940) = 20,340c.p.s.

When the received tone is beat against the fixed frequency tone of 20,000 c.p.s., the difference signal of 340 c.p. s. signals the driver that he is exceeding the speed limit. Since the same pitch is generated for a less than limit vehicle speed, the driver can determine his relative speed by the direction of the change in the pitch. The signal decrea...