Communication system

Details Communication system Communication system

1997-09-19

2003-03-25

Zimmerman, Brian (Department: 2635)

Communications: electrical

Selective

Intelligence comparison for controlling

Reexamination Certificate

active

06538558

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication system, and more particularly, to a communication system comprising one or more remote control transmitters and a single receiver disposed inside a mobile body such as a car wherein in response to reception of various kinds of switching information transmitted from a remote control transmitter, the receiver selectively controls a controllable device provided in the mobile body such as a car, depending on the kind of switching information received.
2. Description of the Related Art
A keyless entry system is a communication system which comprise one or more remote control transmitters and a single receiver disposed inside a mobile body such as a car wherein in response to reception of various kinds of switching information transmitted from a remote control transmitter, the receiver selectively controls a controllable device provided in the mobile body such as a car, depending on the kind of switching information received.
FIG. 5
is a simplified block diagram illustrating an example of such a keyless entry system disclosed in Japanese Examined Patent Publication No. 7-71337.
As shown in
FIG. 5
, this keyless entry system includes three, remote control transmitters
41
-
1
,
41
-
2
, and
41
-
3
and a single receiver
42
disposed inside a car.
The three remote control transmitters
41
-
1
through
41
-
3
each include: a transmitting circuit
43
-
1
,
43
-
2
, or
43
-
3
for generating a transmission signal; an identification data memory (ROM)
44
-
1
,
44
-
2
, or
44
-
3
for storing identification data R-
1
, R-
2
, or R-
3
uniquely assigned to the respective transmitters
41
-
1
,
41
-
2
, and
41
-
3
; and a transmitting antenna
45
-
1
,
45
-
2
, or
45
-
3
.
The receiver
42
includes: a receiving circuit
47
for receiving a signal via a receiving antenna
46
, amplifying the received signal, and further shaping the waveform of the amplified signal; a signal processing unit
48
for performing various control operations in various operation modes; a memory (EEPROM)
49
for storing the identification data R-
1
, R-
2
, and R-
3
; a setting switch circuit
50
including two switches
50
-
1
and
50
-
2
for setting the operation mode of the signal processing unit
48
to either a normal mode, writing mode, or an erasing mode depending on the on/off states of the switches
50
-
1
and
50
-
2
; a door controller
51
for locking and unlocking the doors of the car; an indicator/alarm
52
including light emitting diodes and a horn, which operates when the operation mode is switched from the writing mode or the erasing mode to the normal mode; and a timer
53
provided in the signal processing unit
48
.
The operation of the keyless entry system having the above construction is briefly described below.
First, the signal processing unit
48
in the receiver
42
is set in the normal mode. That is, the two switches
50
-
1
and
50
-
2
of the setting switch circuit
50
in the receiver
42
are both maintained in open states.
In this situation, if one of the three remote control transmitters
41
-
1
,
41
-
2
,
41
-
3
, for example the remote control transmitter
41
-
1
is operated, the transmitting circuit
43
-
1
of the remote control transmitter
41
-
1
generates a control signal (FSK signal) containing a command of locking or unlocking a door of the car and also containing the identification data R-
1
read from the identification data memory
44
-
1
. The generated control signal is transmitted via the transmitting antenna
45
-
1
as a transmission signal at a radio frequency (RF).
In the receiver
42
, the receiving circuit
47
receives via the receiving antenna
46
the transmission signal transmitted from the remote control transmitter
41
-
1
. The received control signal is amplified and waveform-shaped, and then supplied to the signal processing unit
48
. The signal processing unit
48
first compares the identification data R-
1
contained in the received control signal with the identification data R-
1
stored in the memory
49
. If these data are identical, the signal processing unit
48
then detects the status of the door of the car via the door controller
51
. If the door is in a locked state, then the signal processing
48
supplies a control signal to the door so as to unlock the door. On the other hand, if the door is in an unlocked state, then the signal processing unit
46
supplies a control signal to the door so as to lock the door.
When it is required to write identification data R-
1
, R-
2
, or R-
3
into the memory
49
, the switch
50
-
1
of the setting switch circuit
50
of the receiver
42
is closed by operator while maintaining the other switch
50
-
2
in the open state, so the operation mode of the signal processing unit
48
of the receiver
42
is set to the writing mode. And the timer
53
is started.
Immediately after setting the operation mode into the writing mode, if one of the three remote control transmitters
41
-
1
,
41
-
2
,
41
-
3
, for example the remote control transmitter
41
-
1
, is operated, a control signal containing the identification data R-
1
read from the identification data memory
44
-
1
is generated by the transmitting circuit
43
-
1
of the remote control transmitter
41
-
1
and is transmitted as a transmission signal via the transmitting antenna
45
-
1
. If the receiving circuit
47
of the receiver
4
receives the above control signal from the remote control transmitter
41
-
1
, the receiving circuit
47
transfers the received control signal to the signal processing unit
48
. The signal processing unit
48
detects the identification data R-
1
from the control signal, and supplies the detected identification data R-
1
to the memory
49
so that the identification data R-
1
is written into the memory
49
. If the count t of the timer
53
has reached a specified value T, for example 5 sec, the indicator/alarm
52
is activated for a short period of time to indicate that the operation mode will be switched, and then the operation mode of the signal processing unit
48
is automatically switched from the writing mode to the normal mode.
When it is required to erase all the identification data R-
1
, R-
2
, R-
3
stored in the memory
49
, only the switch
50
-
1
of the setting switch circuit
50
of the receiver
42
is first closed by operator while maintaining the other switch in the open state, and the timer
53
is started, and immediately after that, the switch
50
-
2
of the setting switch circuit
50
is also closed. So the operation mode of the signal processing unit
48
of the receiver
42
is set to the erasing mode.
If the switches
50
-
1
and
50
-
2
are set in the above-described manner, all the identification data R-
1
, R-
2
, R-
3
stored in the memory
49
are erased. After completion of the erasing of the identification data R-
1
, R-
2
, R-
3
, the indicator/alarm
52
is activated for a short time so as to indicate that the contents of the memory
49
have been erased. Then the operation mode of the signal processing unit
48
automatically returns from the erasing mode to the normal mode.
The memory
49
has a plurality of (k) memory areas, so that a plurality of identification data R can be stored in these memory areas. The respective identification data R are stored in the memory
49
in such a manner that one identification data is stored in one memory area and another identification data is stored in another memory area. If k+1 or more identification data R are written, the oldest identification data R is replaced by the newest identification data R each time identification data is input.
In the conventional keyless entry system, when one of remote control transmitters
41
-
1
,
41
-
2
,
41
-
3
is lost, it is possible to erase all the identification data R-
1
, R-
2
, R-
3
, which are uniquely assigned to the respective remote control transmitters including the lost one, from the memory
49
of the receiver
42
. This allows the keyless ent

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