Combination electronic road guidance and communication system for vehicles

An automobile equipped with the vehicular portion of a traffic information and guidance system utilizing exchange of data between vehicles and the rest of the system through inductive coupling with loops set at various places in roadways, is provided with two-way telephone communication possibilities at places where roadway loops are provided where a car can stop for making a telephone call, as for example in a parking space. Only small amounts of equipment need to be added to the vehicle and to the fixed installations to permit telephone communication between the vehicle and telephones in a public network. Separate receivers and transmitters for speech communication operated with amplitude or frequency modulation can be switched in, or else the speech signals can be converted into pulse code modulation and simply supplied through input/output units to the data transmitter/receiver of the traffic information system. The telephone calling features are enabled only when the travel path measuring device of the traffic information system is at rest, but the vehicle can be reached while in motion by a paging system to ask the driver to stop at the next telephone communication location.

This invention concerns the incorporation of vehicular telephone 
communication facilities in an inductive digital electronic route and 
destination guidance system, so that vehicles may economically be provided 
both with guiding advice towards their destinations and with the 
capability of connection to a public telephone system without leaving the 
vehicle. 
An inductive traffic guidance system for helping drivers of vehicles to 
reach the destinations they select and enter into an apparatus in the 
particular vehicle is disclosed in German published patent application 
(OS) No. 25 15 660. In that system, loops for electrical inductive 
communication are built into road surfacing at various locations. If a 
vehicle drives over such a road loop, information is transmitted between 
the vehicle and a communication station, the vehicle driver first 
transmitting his destination and the communication station then providing 
him information of importance to him, such as indication of direction to 
travel, road conditions, suitable speed, and the like, this information 
being transmitted automatically and being displayed in the vehicle on a 
visible display. Such guidance to destination systems for vehicular 
traffic are also disclosed in European patent application No. 79 100 
732.1, and in the following articles: "ALI System for Destination Guidance 
and Traffic Data Provision", Radio Mentor Elektronik, Vol. 44, No. 3, 
(Berlin, 1978) pp. 103-108, and "Elektronik Sign Post for Auto Drivers", 
NTZ, Vol. 28, No. 8 (1975), pp. 306-308. The known systems have the 
disadvantage that a reply by the vehicle driver for transmitting 
information other than destination is not possible. 
Computer controlled telephone systems are also known, such as, for example, 
the system produced by the Bosch company under the designation OF4D. These 
computer controlled telephone systems utilize a transmitter and a receiver 
making possible radio contact to a relay station. Signal transmission 
usually takes place in the ultra-high frequency range. These known radio 
telephone equipments are very expensive, however, and are also unreliable, 
because on the one hand much complication and expense must be devoted to 
the privacy of the transmission and on the other hand, only few frequency 
ranges are available for these transmissions, so that the radio telephone 
customer often finds no free channels. A further disadvantage of computer 
controlled radio telephone systems is that even limited privacy is far 
from completely assured. 
It is an object of the present invention to provide inexpensive means for 
communication between vehicles and fixed telephone stations, especially 
telephones of a general public telephone network, whenever the vehicle is 
equipped with a traffic information and guidance system of the kind 
already mentioned. 
Briefly, at least some of the roadway transmitter/receiver installations of 
the traffic information and guidance system are set in parking and/or 
roadside pause areas for exchange of signals with temporarily stationary 
vehicles. In one embodiment of the invention, separate 
transmitter/receiver facilities are connected to the vehicle loop and to 
the street loop for transmitting analog speech signals by amplitude or 
frequency modulation of a carrier frequency. In another embodiment, the 
speech signals are transmitted digitally. The station selection (dialing) 
signals and the supervisory signals for telephone conversations can be 
provided as tones in the speech channel or they may be handled, at least 
prior to establishment of a telephone connection, through the digital 
signals of the traffic information and guidance system. Since the 
inductive communication part of the connection, like a radio link, is a 
so-called "four wire" telephone circuit, the usual two-wire to four-wire 
circuits and vice versa, known as "hybrids" or "termination sets" for 
short, are necessary for the two-way telephone connection, as is well 
known in telephone practice. Preferably, when the speech transmission is 
digital, one digital word or "byte" is sent alternately in each direction, 
thus providing a time division channel in each direction continuously. 
The system of the invention has the advantage that an already provided 
traffic information and guidance system provides the inductive loops and 
much other equipment that can be used for telephone communication as well 
as for the traffic information and guidance and, furthermore, that the 
inductive system offers the possibility of accommodating more than one 
two-way speech channel. The additional equipment necessary for telephone 
communication is much less expensive than what is necessary for the usual 
mobile radio installation, thus offering possibilities of great expansion 
of telephone communication with vehicles. Furthermore, the system has 
inherent protection of privacy, because the inductive field used for the 
vehicular link operates at low power and falls off in intensity with 
distance with a much greater rate than a radio signal field. It is 
particularly advantageous to utilize the possibilities of speech 
communication offered by the invention beyond the limits of the traffic 
information and guidance system and traffic control personnel and to 
extend it even to connection with the public service telephone 
communication system of the particular country or area. 
The supervisory frequencies for telephone communications can advantageously 
and readily be derived from the clock frequency of the traffic information 
and guidance system, and likewise selective calling tones or pulses. 
For charging of telephone system tolls and for mitigating misuse of the 
system, it is advantageous to provide for interrogation of the vehicle by 
the fixed system and the furnishing of an identifying code by the vehicle 
equipment before the setting up of a telephone connection. The 
vehicle/user code can also be used in automatic message accounting of the 
telephone system for accounting and billing purposes. Where the European 
system of charging by means of pulse counting prevails, the charges for 
each call can of course be accumlated in the vehicle as well as in the 
fixed telephone service installation. 
The most economical embodiment of the invention for utilizing the 
vehicle-mounted equipment used for traffic information and guidance 
involves merely adding an additional transmitter and an additional 
receiver, connected to the same inductive transmitting and receiving loop, 
arranged for being switched in for speech transmission. This additional 
transmitter and receiver will be controlled by supervisory signals derived 
from the clock pulses of the traffic information system and transmitted 
and received in accordance with usual telephone practice. The additional 
transmitter and receiver can advantageously operate with frequency 
modulation or amplitude modulation. On the other hand, the possibility of 
subjecting the speech signals to conversion into digital form and back 
involves a minimum of modification of the traffic information and guidance 
equipment. In this case, it is advantageous to provide registers in which 
the converted signals can be stored. That makes it easy to send stored 
signals alternately in each direction and avoiding the necessity of using 
push-button or voice-operated equipment for directional control. It is 
also advantageous to have a travel detector in the vehicle so that the 
telephone communication mode of operation can be switched in only when the 
motion detector indicates that the vehicle is stopped. In fact, it is also 
possible to block the setting of the vehicle into motion until the 
telephone communication is completed in order to avoid interruption of the 
telephone connection without the provision of the usual supervisory 
disconnect signal. It is of course advantageous to utilize a microcomputer 
that may be in the traffic information and guidance unit of the vehicle to 
store telephone numbers and to operate automatic repetition of called 
numbers. It is also advantageous to equip the combined traffic and 
telephone system of the vehicle with a receiver serving a regional paging 
system, so that the driver of the vehicle will be notified of a telephone 
number to be called at the next opportunity offered by the system of the 
present invention. In Europe this means the installation of a 
"Euro-signal" and provision for displaying or announcing attempts to reach 
someone in the particular vehicle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Traffic information and guiding systems for expressways and other main 
highways have been known for a long time. In one known system of this sort 
which has been made available to the public under the designation ALI, 
induction loops are built into the roadways. These induction loops are 
located either in the surface of the highway or else in parking areas and 
expressway entrance ramps. A process computer is connected in each case to 
the induction loop and is itself connected by data connections to a 
central computer. In this way the flow of traffic can be optimized by 
accumulating and distributing traffic information and thereby influencing 
the flow of traffic. Contact with the automobile driver is completed 
through a vehicle-mounted device to which the output information is 
communicated through the induction loop. Information flows in both 
possible direction. The driver must before going into the system enter his 
destination in the form of a decimal number into the vehicle-mounted 
apparatus. When he drives over an induction loop the vehicle mounted 
apparatus is activated and these data are transmitted to the process 
computer which acts as a satellite or peripheral device for the central 
computer. The process computer then makes available for the individual 
case how the driver of the vehicle can reach his particular destination by 
the way which is shortest in time. 
The principle of interactive transmission is based on the fact that with a 
transmitter, receiver, destination entry keyboard and optical display 
field, as well as a vehicle equipped with a special antenna (typically or 
ferrite rod), a vehicle can automatically announce its presence and 
destination when it enters the operating region of the system. The 
information is first picked up in an induction loop and then transmitted 
by wire to an apparatus located adjacent to the roadway (which may be 
referred to as the road apparatus). The road apparatus has a microcomputer 
equipped with a store, from which the prescribed directional 
recommendation corresponding to the particular intended destination of the 
vehicle are obtained and transmitted back to the vehicle over the same 
induction loop. The directional recommendations also contain speed 
recommendations as well as announcements and warnings regarding traffic 
accumulation or jams and any risks of fog and/or ice. Complete details 
about the practical construction of the vehicle equipment as well as the 
roadway loops and roadside computer installations are obtainable in the 
publications already mentioned above and also in the BMFT report (Bericht) 
"Felderprobung eines Zielfuhrungs- und tionssystems fur Autofahrer (ALI)". 
Building on the base of such a system it ought to be possible in principle 
to receive and to send data other than information relating to traffic by 
means of the transmitting and receiving unit in the motor vehicle. This is 
the starting point of the invention, leading to the possibility of 
modifying the data transmitting and receiving unit for traffic information 
so that it can also be used for transmitting telephone conversations or 
other information. 
Whereas the traffic information takes place, and to some extent must take 
place, during travel of the vehicle past particular places, it is possible 
to make a wireless connection to the public telephone network by means of 
loops that are located under marked parking places or on paved shoulder 
strips of a roadway or other publicly accessible areas, so that telephone 
conversations may be possible from a motionless vehicle. 
The stationary telephone and data station, accordingly, instead of having a 
telephone booth into which a person would have to go after leaving his 
car, consists of a loop disposed under the roadway or parking space 
surface and supplementary equipment for transmitting speech communication. 
The vehicle-mounted equipment includes supplementary equipment making 
possible speech transmission through the vehicle equipment. These 
respectively fixed and mobile installations convert the usual signals of 
speech transmissions on both sides of the inductive link into a form that 
assures reliable transmission through the traffic information system. To 
complete the equipment, as already mentioned, it is convenient to provide 
enablement of the speech communication equipment only when the vehicle is 
stationary and to equip the vehicle with a paging receiver so that the 
vehicle drive can also be "paged" as he travels on the road and asked to 
call a particular place or number. The driver then drives to the nearest 
parking space that is designated as a telephone loop parking space. 
Displacing the telephone instrument in the vehicle initiates the search 
for a free channel, where, as soon as correct and reliable signal 
transmission has been found to have been established, the usual dial tone 
or other indication of readiness is provided. Then the conventional 
dialing of the called party is performed, the conversation carried on in 
the usual way and then terminated. The necessary toll information is 
generated in the apparatus associated with the loop, or, if the pulse 
method of charging for calls which is prevalent in Europe is in effect, 
the number of toll units used can be registered in the vehicular 
equipment, in the roadway equipment, or both. 
The vehicle on-board equipment can include, in addition to the telephone, 
all devices which have already been introduced into stationary telephony 
(e.g. picture screen text apparatus). The system is extendable to all 
apparatus which can be connected to the public telephone network. 
THE FIRST ILLUSTRATED EMBODIMENT 
FIG. 1 shows equipment built into a vehicle which can function for the 
transmission of telephone conversation as well as for the reception and 
transmission of traffic information. The normal traffic information 
vehicle equipment contains a microprocessor 1 that is provided with stores 
both for its program and for data. This microprocessor 1 has access over a 
control bus to a display and input unit 3, to a transmitter-receiver 4 
readily switchable from transmission to reception and back, to 
input/output units 2, 10 and 11, to clock pulse preparation circuits 9, to 
a transmitter 7 and a receiver 8. The component groups just named are 
connected with the data bus 13 of the microcomputer through input/output 
units 2, 10 and 11. The transmitters and receivers 4, 7 and 8 are also 
connected to a ferrite antenna 5 which serves for data transport between 
it and the loop of the roadway equipment set in the roadway. In addition, 
a travel path transmitter 6 which produces signals from which the vehicle 
motion can be measured is connected with the input/output unit 11. Apart 
from the components 7, 8 and 9 the various components shown are contained 
in every traffic information apparatus of the ALI type and are described 
in detail in the publications cited above. The transmitter 8 and the 
receiver 7 are additions to the system which are necessary for connection 
of a telephone to a traffic information loop apparatus. This transmitter 
and this receiver utilize the same ferrite antenna as is used by the 
transmitter/receiver unit 4 of the traffic information apparatus. 
FIG. 2 shows the roadway apparatus for connection of the vehicular 
telephone with the public telephone network. The microcomputer 20 of the 
loop apparatus is connected through a control bus 28 with the input/output 
unit 21, the transmitter/receiver 22, a transmitter 24, a receiver 25, a 
timing pulse preparation unit 31 and a selecting device (dial or tone-pad) 
27. The data bus 29 is connected with the selector 27, the clock pulse 
preparation unit 31 and, through the input/output unit 28 with the 
transmitter/receiver 22. The transmitter/receiver 22 corresponds to a 
normal traffic information loop apparatus. The transmitter/receiver 22 is 
connected with the loop 23. For telephone connections, the transmitter 24, 
the receiver 25 and the pulse preparation circuit 31 are necessary just as 
in the case of the vehicular equipment. The transmitter 24 and the 
receiver 25 are interconnected by a 4-wire terminating set 26 that 
provides a conventional transition from a two-wire circuit to a four-wire 
circuit. The four-wire terminating circuit provides the necessary split 
into the output and return channels necessary for talking back and forth. 
Such circuits are well known in telephone practice and have been developed 
in a large variety of well-known circuits. They make possible avoidance of 
voice-operated or manual directional switching and are balanced to avoid 
the generation of oscillations or echoes. The selection device 27 is also 
necessary for effective connection of the system to telephone lines. The 
generation of the dial pulses is performed by the microcomputer 20 of the 
loop-connected equipment and for this purpose that equipment is connected 
over the control bus 28 and the data bus 29 to the selector 27. 
A telephone connection takes place as follows. If the automobile driver 
intends to make a telephone call, he drives into the next parking place 
that has a built-in telephone loop. As soon as the vehicle comes to a 
stop, as is recognized by the travel path transmitter 6, the microcomputer 
20 of the stationary loop equipment sends out call pulses such as are 
normal in the operation of a traffic information system which has been 
approached by a vehicle. The number of these "stepping" pulses can be 
greatly reduced compared to the usual traffic information system practice. 
It is enough to have about one call step pulse per second. When the driver 
is located on a recognized loop position and has come to a stop with his 
vehicle, he picks up the telephone handset 14 of the vehicle equipment, 
which is in turn connected to the transmitter 8 and the receiver 7. The 
microcomputer 1 of the vehicle equipment now answers to the next call step 
pulse of the loop-connected equipment, with a data "telegram" such as is 
known from traffic information system transmission practice. Only the key 
word, for example in byte 1 of the telegram, is altered. The vehicle 
number and the private telephone number of the driver can now be 
transmitted for toll charging purposes in the normal traffic information 
system mode of operation. For additional security, it is possible, for 
example, to transmit a code word in the form of a multispace decimal 
number. The microprocessor 20 of the loop-connected equipment now awaits 
the dial tone of the central office which it will receive through the 
selector 27 that is connected through the line 30 to the public telephone 
network. The dial tone is now transmitted to the vehicle over the data 
channel of the traffic information system. 
The vehicle driver can now enter the desired called party telephone number 
by means of the keyboard of the unit 3. It is also possible to provide 
frequently called numbers in a store of the microprocessor 1, from which 
they can be called out to increase the ease of operation of the vehicular 
telephone. The desired called party number is then transmitted over the 
traffic information channel to the microcomputer 20 of the loop-connected 
equipment. The latter then starts the normal dialing or tone calling 
process in the selector 27. It is useful to incorporate an automatic 
redialing procedure in the event that a busy signal is received during or 
after the selection operation. 
When the call recognition is sent from the central office, the 
microcomputer 20 of the roadway loop equipment provides this information 
over a data channel of the traffic information system to the vehicular 
equipment. Then the microcomputer 1 of the vehicular equipment and the 
microcomputer 20 of the loop equipment switch out the traffic information 
transmitter/receiver 4 and 22 and switch in the transmitters 8 and 24 and 
the receivers 7 and 25. A direct connection to the telephone instrument is 
thereby established from the telephone line, through the selector 27, over 
the four-wire terminating circuit 26 and over the transmitter and 
receiver. What follows is the same as in the case of a normal telephone 
conversation. The microcomputers of the vehicular equipment 1 and of the 
loop equipment 20 respectively check through their receivers 7 and 25 
whether the connection still exists. If the automobile driver or passenger 
puts the telephone instrument back in its resting place, the vehicle 
microcomputer 1 switches the transmitter 8 off and the microcomputer 20 of 
the loop equipment recognizes by a missing reception signal the 
termination of the telephone conversation and goes back into the mode for 
data exchange for traffic information. At the same time it interrupts the 
connection to the telephone line through the selector apparatus 27. 
In the case of termination of the telephone conversation by the remote 
party, the microcomputer 20 of the loop equipment recognizes the 
termination of the telephone conversation through the selector 27. It 
switches the transmitter 27 off and switches on the transmitter/receiver 
component group 22. The microcomputer 1 of the vehicle equipment now 
recognizes the breaking off of the telephone connection by the absence of 
the reception signal. The vehicle driver or passenger is then urged to 
replace the telephone instrument on its stand or hook by the provision of 
an optical and/or an acoustic signal. 
After the telephone connection is broken off, the loop-connected equipment 
goes back into the call step mode and the loop is free for other telephone 
connections. 
THE SECOND ILLUSTRATED EMBODIMENT 
Instead of the analog transmission of the telephone conversation, it is 
also possible to provide digital transmission of speech. FIG. 3 shows an 
example of the vehicular equipment in such a case. The combined vehicular 
equipment for telephone communication and traffic information transmission 
again contains the microprocessor 40 necessary for the normal traffic 
information transmission. The microprocessor 40 is connected by a control 
bus 53 with input/output units 41, 42 and 43. The control bus 53 continues 
on to an analog-to-digital converter 49, a digital-to-analog converter 50, 
a register 51, a register 52 and to input/output units 44 and 45. The data 
bus 54 leads from the microprocessor 40 through the input/output unit 41 
to a keyboard and display unit 46 and to the input/output units 42, 43, 44 
and 45. A transmitter/receiver 47 has a transmitter output and receiver 
input connected to a ferrite antenna 51 and is controlled by the 
input/output unit 42. The travel path transducer 6 is connected to the 
input/output unit 43. A telephone handset 48 is connected to the A/D 
converter 49 and the D/A converter 50. 
The digital converter groups 49 and 50 and the registers 51 and 52 now take 
the place of the component groups necessary for the analog connection in 
the first embodiment shown in FIG. 1. The analog-to-digital converter 49 
includes a microphone amplifier, a low-pass filter with a cut-off 
frequency of 3.4 kHz and a sample-and-hold circuit for 8 kHz. It processes 
a signal 8-bit wide in accordance with the CCITT standard. The digital 
values formed to correspond to the analog signal are supplied to the 
register 51. The digital-to-analog converter 50 includes, in addition to a 
digital-to-analog converter according to the CCITT standard, a low-pass 
filter of 3.4 kHz cut-off frequency and an amplifier for driving the 
telephone receiver. The manner of operation of this collection of circuits 
will presently be described in connection with the loop-connected 
equipment shown in FIG. 4. 
The microprocessor 60 is connected to its control bus 61 and its data bus 
62 and with the other component groups of the loop-connected equipment. 
Registers 67 and 68 are controlled through input/output circuits 63,64 and 
65. These registers are respectively connected with an analog-to-digital 
converter 69 and a digital-to-analog converter 70. A four-wire terminating 
circuit 71 is connected to the converters 69 and 70. A telephone line 73 
leads from the selector device 72 over to a telephone central office not 
shown. A transmitter/receiver 66 is provided, to the output of which the 
loop 74 is connected. 
The setting up of a telephone connection takes place with reference to the 
selection operation as already described. When the call signal is 
recognized over the telephone line by the selector 72, the microcomputer 
60 of the loop-connected equipment provides to the vehicular equipment a 
special code word over the traffic information channel. The microcomputers 
40 and 60 of the vehicular equipment and of the loop-connected equipment 
now switch over the transmitter/receiver groups 47 and 72 to FFSK (fast 
frequency shift keying). In consequence, 8-bit words are alternately 
exchanged over the transmitter/receiver component groups 47 and 72 between 
vehicle and roadway loop, the 8-bit words being exchanged alternately from 
the register 51 to the register 68 and from the register 67 to the 
register 52. 
Since the data rates in the FFSK mode can reach as much as 96 k bits per 
second and an 8-bit wide word is intermediately stored in each of the 
registers, a quasi continuous data transport in both directions in each 
case of 48 k bits per second, takes place, which corresponds to the CCITT 
recommendatons. The transmission of speech thus takes place over the data 
transmission channels that otherwise are used for transmitting the traffic 
information. Separate apparatus modulated in an analog manner are 
therefore not necessary in this embodiment. 
Although the invention has been described with reference to particular 
illustrative examples, it will be understood that modifications and 
variations are possible within the inventive concept. For example, the 
vehicle speedometer may be equipped to indicate when the vehicle is 
standing still, instead of the vehicle travel measurement device usually 
included in an "ALI" traffic information system.