SYSTEM FOR WARNING OF TRAFFIC INCIDENTS

Abstract: System for warning of traffic incidents, especially the approach of emergency vehicles, comprising a radio transmitter adapted to be positioned in a first vehicle, e.g. an emergency vehicle, and a radio receiver adapted to be positioned in a second vehicle. Said transmitter is adapted to emit radio frequency pulses within a chosen frequency range, at chosen intervals being substantially longer that the duration of the pulses, and said receiver is adapted to receive radio signals within said chosen frequency range and to detect the occurrence of said pulses, the receiver also comprising means for visually or audibly indicating the detection of said signals.

Description: SYSTEM FOR WARNING OF TRAFFIC INCIDENTS. This invention relates to a system for warning of traffic incidents, especially the approach of emergency vehicles . In traffic emergencies and emergency vehicles sirens are often used to warn a nearby driver of a possibly dangerous situation. Because of the increasing use of car stereos and cellular phones, as well as improved sound proofing, it has become a common problem in cars that drivers do not hear an approaching emergency vehicle, such as an ambulance. Thus the ambulance is delay, with possible fatal results. Further, dangerous traffic conditions may arise where an unwarned driver obstructs an emergency vehicle which is often travelling at high speed. Several systems have been suggested in order to warn the drivers of a dangerous situations in the traffic, many of them comprising radio transmitters positioned in an emergency vehicle. Receivers adapted to detect the generated signal are provided in ordinary vehicles, so that the receiver may generate a signal warning the driver. Examples of such systems are described in the following patents: US 4,238,778, US 4,403,208, and US 4,764,978. In addition to the examples shown in the abovementioned patents there are a large number of other suggested systems . Most of these use a radio transmitter using a chosen frequency to transmit a coded signal. An important drawback with this solution is that it is difficult to use the same frequency throughout a country or region, because of the multitude of radio channels using different frequencies in different regions. To provide a secure system a chosen radio frequency must be reserved to this use. This is a problem because of the large demand from different radio stations, cellular phones, communication channels etc. Another alternative is to provide for an automatic change in the listening frequency of the receiver, as has become usual to some radio stations and systems. This does not, however solve the problem of occupying at least one radio frequency in each region, and also gives a complicated and expensive solution. It is an object of this invention to provide a system for warning of traffic incidents comprising a radio transmitter adapted to be positioned in a first vehicle and a radio receiver adapted to be positioned in second vehicle, characterized as described in claim 1. The invention provides a system for transmitting signals from e.g. an emergency vehicle to a driver using radio signals, but without occupying a radio frequency, as the pulsed signal does not disturb normal radio signals. This way the same frequency range may be used everywhere, making both the transmitters and the receivers simple and possible to produce at low costs. The invention will be described below with reference to the accompanying drawings, showing one possible embodiment of the invention. Figure 1 shows schematically a diagram of a transmitter according to the invention. Figure 2 shows schematically a diagram of a receiver according to the invention. The transmitter unit in figure 1 comprises a oscillator 1, preferably being of a high stability, temperature compensated type. It may be a synthesized solution with a stable reference oscillator or a crystal oscillator with a frequency multiplier. The circuit also contains an amplifier which brings the radio frequency (RF) signal to a level required by the power amplifier 5. Normally the oscillator 1 will work continuously while the transmitter unit is turned on. The frequency of the signal generated by the oscillator may be chosen from a wide range. In a preferred embodiment the frequency is approximately 750MHz. A radio frequency (RF) switch 2 is controlled by a control/timer unit 3 through a connection 4, and makes sure that the RF signal from the oscillator only reaches the power amplifier in short bursts. The isolation through the switch between the bursts must be high enough to satisfy the EMC requirements of this kind of equipment . If there should be difficulties in achieving a sufficient degree of isolation in the RF switch alone a DC switch 6 adapted to switch of the power amplifier 5 may be implement- ed. The RF switch 2 may comprise one or more monolithic RF switch circuits of any suitable type, or may be based on discrete solutions with PIN diodes etc. In order to avoid interference with usual radio signals in the chosen frequency range the ratio between the duration of each pulse, and the interval between the pulses may in the order of 1/10000. For example, the pulses may have a duration of lOOμs and be sent at Is intervals. This may, however, be varied to a large degree. It is also possible to distinguish between different types of transmitters, e.g. positioned in different types of vehicles, by changing this ratio, the duration of each pulse, and/or the interval between the pulses according to the vehicle it is to be position in, or the warning to be sent. Thus a driver may be able to distinguish between an ambulance, a police car or another type of traffic incident. The RF power amplifier 5 may be of any suitable type, based on monolithic, hybrid or discrete circuits. It must be capable of providing a sufficient level of RF signal to give the signal a sufficiently large range. The range may be in the order of 100 metres, depending of the intended use. The range will of course also depend on the receivers, as well as the antenna. The abovementioned control unit/timer unit 3 controls the RF switch through the timer output 4 and thus the timing of the signal bursts, as well as the optional DC switch 6, also connected to the timer output 4, which in turn controls the RF power amplifier 5. The control/timer unit also provides other parts of the transmitter unit with necessary power through the connections 8, and may be connected with conductors 10 to the battery of the vehicle. The antenna 9 may be of any suitable kind, directive or not, depending on the intended use. In addition to being mounted on emergency vehicles the transmitter may be implemented in other cars or in warning signs for use in especially dangerous situations. The transmitter may be contemplated mounted in ordinary cars connected to a detector adapted to detect collision, such as the ones used in air bags. This way the transmitter is started at once, warning other drivers of an accident at the movement it happens. Receivers positioned along dangerous parts of the road may detect accidents and transmit the signal to the police, the nearest hospital etc, thus saving time and perhaps lives. Figure 2 shows schematically the receiver unit according to a preferred embodiment of the invention. An antenna 11 of any type capable of receiving signals within the chosen frequency range is connected to a RF filter 12. The RF filter discriminates the wanted radio frequency from interfering signals from mobile telephones or other strong signal sources. The signal rejection capacity must be so high that no known and expected signal source can reduce the receiver functions significantly. These specifications may be chosen according to the allowed percentage of false alarms. The filtered signal is amplified in a RF amplifier 13 to provide a high grade of receiver sensitivity, and is mixed in a mixer 14 with signals from a local oscillator 15. The resulting, intermediate frequency (IF) may be chosen to be a relatively low frequency, e.g. 455kHz, where it is easy to detect . In normal receivers for audio communication etc there is an image frequency filter in front of the mixer. This is done to make sure that the receiver only has one response frequency. If this is done in the present inven- tion the intermediate frequency (IF) may be chosen to be higher, e.g. 70MHz. In order to make a more simple and less expensive receiver one unwanted, spurious frequency may be allowed, since the presence of this frequency with sufficient strength to cause malfunctions is considered to be rare. The local oscillator may me a synthesized solution with a stable, temperature compensated crystal oscillator with a frequency multiplier. The frequency of the oscillator is RF minus IF. The mixed signal is filtered in a first IF filter 16, which may comprise ceramic filters with a very high rejection capacity. The first IF filter 16 ensure that unwanted signals close to the wanted signals are rejected and do not cause malfunctions or false alarms. The signal is then amplified to a detectable level in a suitable amplifier 17. Monolithic or discrete amplifiers with low noise factors are preferably used, with an gain preferably in the range of 100-110 dB. A second IF filter 18 is provided to filter the signal again before it reaches the detector 19. The detector is adapted to rectify and integrate the IF signal, and also to determine if the burst lengths are within allowed tolerances. It may also be adapted to distinguish between different types of signals, in order to give the driver the correct type of warning. If a signal is detected the detector generates a warning signal to a suitable display or an acoustic device, or possibly to a control unit 20. The control unit 20 in the receiver has two main functions according to the shown embodiment: to provide the other circuit parts with the required supply voltages, and to generate control signals to indicators when an admitted detection has taken place. To decrease the possibility for false alarms a condition is built into the system demanding at least two bursts with a defined interval before the indicators are activated. This may decrease the chance of false alarms with a factor of more than 1000. The control units and the detector described here comprises electronic circuits for time measurements and possibly counting of pulses. These circuits are well known and commercially available, and the exact embodiments of them are not essential to this invention. Other embodiments of the invention, using other components, such as using other types of pulse emitters or detectors, may of course also be contemplated within the scope of this invention.

Claims: C l a i m s 1. System for warning of traffic incidents, especially the approach of emergency vehicles, comprising a radio transmitter adapted to be positioned in a first vehicle, e.g. an emergency vehicle, and a radio receiver adapted to be positioned in a second vehicle, c h a r a c t e r i z e d in that said transmitter is adapted to emit radio frequency pulses within a chosen frequency range, at chosen intervals being substantially longer that the duration of the pulses, and that said receiver is adapted to receive radio signals within said chosen frequency range and to detect the occurrence of said pulses, the receiver also comprising means for visually or audibly indicating the detection of said signals. 2. System according to claim 1, c h a r a c t e r i z e d in that the occurrence of pulses are indicated as a result of the detection of at least two pulses with a chosen time interval. 3. System according to claim 1 or 2 , c h a r a c t e r i z e d in that the ratio between the duration of each pulse and the interval between the pulses are in the order of 1/10000. 4. System according to claim 1, 2, or 3 c h a r a c t e r i z e d in that the duration of each pulse is approximately lOOμs, and that the interval between the pulses are approximately Is . 5. System according to one of the preceding claims, c h a r a c t e r i z e d in that the pulses are transmitted in the frequency range of approximately 750MHz, with a band width in the range of 1-lOkHz. 6. System according to claim 1 or 2 , c h a r a c t e r i z e d in that the duration of each pulse, the interval between the pulses and/or the ratio between them, is chosen in relation to the type of vehicle, e.g. an ambulance, a police-car etc. AMENDED CLAIMS [received by the International Bureau on 10 May 1999 (10.05.99); original claims 1-6 replaced by amended claims 1-5 (1 page)] 1. System for warning of traffic incidents, especially the approach of emergency vehicles, comprising a radio transmitter adapted to be positioned in a first vehicle, e.g. an emergency vehicle, and a radio receiver adapted to be positioned in a second vehicle, c h a r a c t e r i z e d in that said transmitter is adapted to emit radio frequency pulses within a chosen frequency range, at chosen intervals being substantially longer that the duration of the pulses, the ratio between the duration of each pulse and the interval between them being approximately 1/10000 or less, and that said receiver is adapted to receive radio signals within said chosen frequency range and to detect the occurrence of said pulses, the receiver also comprising means for visually or audibly indicating the detection of said signals. 2. System according to claim 1, c h a r a c t e r i z e d in that the occurrence of pulses are indicated as a result of the detection of at least two pulses with a chosen time interval. 3. System according to claim 1 or 2 , c h a r a c t e r i z e d in that the duration of each pulse is approximately lOOμs, and that the interval between the pulses are approximately Is . 4. System according to one of the preceding claims, c h a r a c t e r i z e d in that the pulses are transmitted in the frequency range of approximately 750MHz. 5. System according to claim 1 or 2 , c h a r a c t e r i z e d in that the duration of each pulse, the interval between the pulses and/or the ratio between them, is chosen in relation to the type of vehicle, e.g. an ambulance, a police-car etc. STATEMENT UNDER ARTICLE 19 In the enclosed amended claims 1-5 the previous claim 3 is moved to the characterizing part of claim 1, thus specifying more clearly the ratio between the duration of the pulses and the duration of the interval between them. The new claims correspond to the claims being allowed in Norway in Office Action dated 25.03.99. According to this invention a system is provided that allows the transmission of radio signals warning of traffic incidents without affecting other transmissions in the same frequency range. Thus is done by transmitting short pulses at long intervals. The cited US 4.794.394 uses a 1000Hz signal with a ration between pulse duration and pulse interval which, according to figure 3, reference number 19, is approximately 1/1. This will be extremely disturbing for other signals in the same frequency range. Thus the signal must be transmitted at certain frequencies which, as stated in the present application, may change in different geographical locations depending on the local radio transmissions. It is an object of this invention to provide a system that allows the use of a standard system without having to change frequency depending on where the user is. US 4.794.394 does not mention the problem or suggest any solutions that may solve it. Thus US 4.794.394 is not relevant to the present application. The only similarity between the cited US 4.626.849 and the present invention is the use of different frequencies to identify different types of vehicles. This is not a major issue in the present invention. The major issue being, as stated above, the transmission of signals without affecting other transmissions in the same frequency range. US 4.626.849 does not mention any features making this possible, or any intention to do so, and thus is not relevant to this application.

Inventors: EVENSEN JAN, ROSENBERG MORTEN, EVENSEN, JAN, ROSENBERG, MORTEN
Applicants: BURST ELECTRONICS AS, EVENSEN JAN, ROSENBERG MORTEN, EVENSEN, JAN, ROSENBERG, MORTEN
Application year: 1998
Main classification: G08G1
IPC codes: G08G1