Telecontrol system with a plurality of functional ranges selected by detection threshold

A telecontrol system for the remote execution of functions comprising actuation of devices in a motor vehicle, for example operation of courtesy lights and locking and unlocking of the doors, comprises a receiver module mounted on the vehicle and an emitter unit carried by the user for transmitting coded radio signals to the receiver module. A data signal configuring circuit of the receiver module has a detection threshold level which is regulated according to predetermined zones of functional ranges between the emitter and the receiver module, around the vehicle, in such a way that a function on the vehicle which is controlled by the emitter is only validated if the emitter is in the appropriate zone of functional range.

FIELD OF THE INVENTION 
This invention relates to a telecontrol system for the remote execution of 
functions comprising the actuation of devices in a motor vehicle. The 
invention lies in particular in the field of telecontrol systems for, in 
particular, controlling access to a motor vehicle. 
BACKGROUND OF THE INVENTION 
Known types of telecontrol system generally include, and as indicated 
diagrammatically in FIG. 1 of the accompanying drawings, a portable 
emitter 10 which is carried by a user, together with a receiver module 20 
which is fitted in a motor vehicle 30. The emitter 10 is so designed as to 
generate a coded wave 10a. A "coded wave" is to be understood to mean a 
wave which carries information or data in the form of a control or command 
signal. Such a coded wave may be produced by radio transmission, light 
transmission, infrared transmission or ultrasonic transmission, though 
this list is not exhaustive. 
The receiver module 20 is so designed as to detect the coded wave generated 
by the emitter, and to decode the latter. When the code generated by the 
emitter 10 corresponds to one or more predetermined codes, the receiver 
causes locking and unlocking of the doors of the motor vehicle 30, or the 
operation of various auxiliary functions of the vehicle, to be carried 
out. 
Telecontrol systems using a coded wave, with radio transmission in 
particular, are of very flexible application, to the extent that firstly, 
the user has no need to orientate the emitter towards the vehicle in order 
to establish transmission, and secondly, the transmission may be 
established at a distance of some tens of meters from the vehicle. 
Generally, in the higher quality systems, the emitter 10 has a set of touch 
keys which are associated with particular functions in the vehicle, for 
example locking of the doors, unlocking of the doors, operation of the 
courtesy lighting or the driving or parking lights of the vehicle, closing 
of the windows, and activation of an alarm. Since each function has its 
own touch key, the size of the portable emitter unit itself is quite 
large, and the presence of too many touch keys detracts from the 
convenience of the user. 
For certain control functions, such as unlocking the doors and closing the 
windows remotely, a high transmission range can be a factor which is 
detrimental to security. Accidental touching of the touch keys of the 
emitter unit could in this connection cause the doors to become unlocked 
without the user being aware of it. 
On the other hand, there are some functions, such as remote control of 
courtesy lights or other lights in the vehicle, which it may be convenient 
or desirable to operate remotely from quite a long distance away, for 
example for the purpose of remote inspection of the vehicle, in a parking 
lot for instance. Under these circumstances, a transmission range of 
several tens of meters is desirable. 
It is thus apparent that with known conventional telecontrol systems, the 
compromise between convenience or use of the telecontrol system on the one 
hand, and security considerations on the other, leads to the choice of a 
transmission range of between 5 and 10 meters. This transmission range 
favors security at the expense of convenience. 
DISCUSSION OF THE INVENTION 
An object of the present invention is accordingly to improve these systems 
by removing the need to make such a compromise, and to reduce the number 
of touch keys in the emitter unit. 
This object is achieved by the provision of a plurality of operating zones, 
or zones of operating range, around the vehicle. In this connection 
reference is made to FIG. 2 of the accompanying drawings, which show a 
near zone F1 around the vehicle and a far zone F2 surrounding the zone F1. 
An authorized zone, F2 or F1 or both, is attributed to each of the 
functions to be actuated in the vehicle. Some functions (here said to be 
of the type F1) can thus only be controlled in zone F1 which is delimited 
by the transition distance D1. On the other hand other functions (here 
said to be of the type F2) can be controlled in zone F2, which is bounded 
by the system transmission range P and the distance D1. 
The system which is the subject of the present invention can also include 
further functional zones delimited by transition distances D2, D3, to 
which functions of type F2, F3 would be associated. For practical reasons, 
however, the description that follows will relate only to a system with 
two functional zones, but by way of example only. 
The invention also provides a system in which a single touch key of the 
telecontrol system (i.e. on the emitter unit) enables a plurality of 
functions on the vehicle to be executed according to the distance 
prevailing between the emitter and the vehicle when the touch key is 
operated. For example, touching key No. 1 may cause the courtesy light to 
be illuminated when the user is in zone F2, but when he is in zone F1, it 
will unlock the doors. 
This system provides both security and convenience in the same telecontrol 
system, and with the use of few touch keys. 
According to the invention, a telecontrol system for remote actuation of 
devices in a motor vehicle, and especially for actuating the locking and 
unlocking of the doors of the vehicle, the system being of the type 
comprising a portable emitter adapted to generate a coded electromagnetic 
wave, and a receiver module located in the vehicle and arranged for 
receiving and decoding the coded electromagnetic wave generated by the 
portable emitter, the latter including a processor, a radio emitter, a 
group of touch keys, and a power supply source in the form of batteries, 
the receiver module having a receiving antenna, a radio receiving circuit, 
a circuit for configuring demodulated signals, a processor for processing 
the data, and an actuating circuit for actuation of the electromagnetic 
devices in the vehicle, is characterized by the fact that the processor 
includes a control means for controlling a detection threshold of the 
circuit for configuring the demodulated signals, whereby to define a 
plurality of zones of functional range around the vehicle. 
A preferred embodiment of the invention, in the case in which the invention 
is applied to radio transmission to a motor vehicle, will be described 
below, by way of example only and with reference to the accompanying 
drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
Given that the level of the HF signal which is received on the antenna of 
the receiver is a function of the distance between the emitter and the 
receiver, and that the variation in this level as a function of distance 
follows a decreasing law as indicated in FIG. 3, it is possible, for a 
given emitter and a given vehicle, to determine the approximate distance 
between the emitter and the vehicle by detecting the signal level of the 
HF signal received. 
Thus, on the level of the received wave (in this example a high frequency 
or HF signal), a high detection threshold is defined which corresponds to 
the transition distance D1 (on the abscissa in FIG. 3 and in the 
corresponding circle in FIG. 2) and a low detection level which 
corresponds to the limiting transmission range P (again indicated on the 
abscissa in FIG. 3, and the corresponding circle in FIG. 2). It is clear 
that it is possible to choose a number of intermediate levels D2, D3 etc. 
between D1 and P, which are determined in advance and which are 
represented by values which are entered in advance in a memory in the 
receiver module 30. 
As shown in FIG. 4, the emitter includes a first processor 100, a radio 
emitter 101, a group of touch keys 102, and a power source in the form of 
batteries 103. 
The receiver module comprises a radio receiving circuit 201 having an HF 
antenna 200, a circuit 202 for processing demodulated signals, a second 
processor 203 for configuring (forming) data signals, and an actuating 
circuit 204 for actuating electromagnetic devices on the vehicle. 
The radio receiving circuit 201 is arranged to amplify and demodulate the 
coded radio wave received on the receiver antenna 200. This radio 
receiving circuit 201 supplies to the data signal configuring circuit 202 
an analog signal which represents the coded message emitted by the emitter 
10. The data signal configuring unit 202 supplies to the processor 203 one 
or more logic data signals which are adapted to the particular method of 
acquisition and decoding of the data in the coded message that are 
employed in the system, according to the application concerned. The 
processor 203 includes means for switching the demodulated signals from a 
detection threshold of the data signal forming circuit 202. Using this 
switching means, the processor 203 controls, by means of a control signal, 
the detection threshold of the data signal configuring circuit 202, in 
such a way that the signal level of the received HF signal can be 
detected. The said control signal works in the following way. 
When the threshold control signal is at logic level 0, the detection 
threshold is adjusted to its low level (see FIG. 7). All the 
electromagnetic signals which are received on the receiver antenna 200, 
which produce at the output of the HF receiving circuit 201 demodulated 
signals at levels which are greater than this low detection threshold, are 
configured by the circuit 202 and entered or made use of by the actuating 
circuit 204. The low detection threshold level thus determines the 
transmission range P of the system. 
When the control signal is at logic level 1, the detection threshold is 
adjusted to its high level (see FIG. 7). All the electromagnetic signals 
received on the receiver antenna 200 which produce, at the outlet of the 
HF receiving circuit 201, demodulated signals at levels which are lower 
than the high detection threshold, are not formed by the circuit 202 and 
are therefore not entered in the processor 203 or made use of by it. The 
high detection threshold level thus determines the transition distance D1 
of the system. 
The processor 203 puts the detection threshold at its low level by default, 
in order that it can receive all the coded waves emitted from the zones F1 
and F2. 
Each time a touch key 102 of the emitter, or a combination of these touch 
keys, is activated, the processor 100 generates a coded wave which is 
composed, as is shown in FIG. 5, partly of coded data A and partly of 
coded data B. The part of the coded data A contains the data for 
identification of the emitter, while the part B contains only elementary 
data for the purpose of verifying that the receiver module is capable of 
receiving them. In particular, the second part of the message is arranged 
to enable the level of the signals received by the receiver module 20 to 
be detected. 
Let us first consider the case in which the emitter is located within zone 
F2. When the emitter transmits a coded wave, the MF receiver 201 supplies 
demodulated signals at a level which is .greater than the low detection 
level of the data signal configuring circuit 202, but lower than the high 
detection level. In the case in which more than two zones of functional 
range are predetermined, the detection threshold switching means of the 
data signal configuring circuit 202 selects the detection threshold level 
which corresponds to the zone of functional ranges associated with the 
command received, as it is represented in the first part of the message. A 
plurality of threshold levels may be recorded or predetermined in 
addition. 
When the coded wave is received, as indicated in FIG. 8, the processor 203 
sets in train the execution of a number of operations for the purpose of 
determining, firstly, the validity of the received coded data, and 
secondly, the device which is to be actuated by the circuit 204. 
The time diagram in FIG. 8 will assist in giving a better understanding of 
the chronological train of events in these operations. The operations 
carried out by the processor 203 are as follows. 
S1: the processor 203 of the receiver module 20 acquires the data in the 
part A of the message transmitted by the emitter 10. 
S2: when the processor 203 has acquired all the data, it decodes them and 
verifies their validity. 
S3: if the processor 203 considers that the data are valid, it activates 
the control signal for the detection threshold of the data signal forming 
circuit 202, in order to shift the detection threshold to its high level. 
S4: after the time necessary for stabilization of the analog signals in the 
data signal forming circuit has elapsed, the processor initiates the 
process of acquiring data from the part B of the message transmitted by 
the coded wave. 
S5: since the demodulated signals provided by the HF receiver 201 are lower 
than the high detection threshold of the data signal forming circuit 202, 
no logic data signal is transmitted to the processor 203. The processor 
thus cannot acquire data from the part B of the message transmitted by the 
emitter. It therefore controls the function F2. 
The case in which the emitter is located in zone F1 will now be considered. 
When the emitter transmits a coded Wave, the HF receiver 201 supplies 
demodulated signals at a level which is higher than both the high and low 
detection thresholds of the data signal forming circuit 202. 
The operations proceed as in the preceding case, up to phase 4, after which 
they proceed in the following way. 
S5: since the demodulated signals supplied by the HF receiver 201 are at a 
higher level than the high detection level of the data signal forming 
circuit 202, the logic data signals are transmitted to the processor 203. 
The processor is thus able to acquire the data in B of the message 
transmitted by the emitter. 
S6: when the processor 203 has acquired all of the data, it decodes them 
and verifies their validity. 
S7: if the processor 203 considers the data to be valid, it then actuates 
the function F1. 
The format of the data message may be different from that indicated in FIG. 
5. The principle claimed in the claims of the present application may for 
example be applied to a message format such as that which is indicated in 
FIG. 6, in which the messages A are repeated at least once. 
The part B of the message may also be reduced to uncoded data.