# US 5,349,459 A · Secure remote control system

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- Number: US 5,349,459 A
- Document ID: US5349459A
- Status: Granted
- Kind: A
- Application number: 07/884,971
- Filed: 1992-05-18
- Granted: 1994-09-20
- Earliest claimed: 1992-05-18
- Assignees: Rockwell International Corporation
- Inventors: Irving S. Reed
- Web page: https://patentgrep.com/patent/US5349459A

## CPC

- H04B 10/00: Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- G08C 19/24: using time shift of pulses
- H04B: TRANSMISSION
- G08C: TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS (fluid pressure transmitting systems F15B; mechanical means for transferring the output of a sensing member into a different variable G01D5/00; mechanical control systems G05G)

## Abstract

A vehicle access transmitter and receiver pair which cooperate to implement a code transmission strategy which requires a minimum amount of energy thereby accomplishing maximum battery life while achieving operations secure from unauthorized access. The transmitter produces a string of start-and-stop pulse pairs which are each spaced in a timed interval so as to represent unique values. In operation the transmitter generates a sequence of four start-and-stop pulses with the duration of start-and-stop pulse pair proportional to the respective key code. The receiver detects the pulses and supplies them to a code comparison circuit. A lock code is stored and supplied to the code comparison circuit. During the reception time between each start-and-stop pulse in a pair, the demodulator counts up sequentially producing a vector sum of the lock code and the received code value. If the vector sum of all code valves stored and received equals zero, then a VALID signal is generated by the code comparison circuit permitting access to the vehicle via the selected path, i.e., Door, Trunk, etc.

## Claims

### Claim 1

A method of providing security for a remote control system which includes a transmitter and a receiver, comprising the steps of:
generating an electromagnetic radiation signal with the transmitter, the signal including a plurality of pulse pairs, each pair including a start pulse and a stop pulse, with the time interval between each start-and-stop pulse being proportional to a corresponding value in a predetermined key code sequence;
detecting the electromagnetic signal with the receiver;
deriving the key code sequence from the time intervals in the received sequence of start-and-stop pulse pairs;
comparing the derived key code sequence to a predetermined lock code sequence; and
generating a valid signal if each value in the derived key code sequence corresponds in a predetermined manner to each value in the lock code sequence by generating a valid signal if each value in the derived key code sequence is the complement of the corresponding value in the lock code sequence.

### Claim 2 (depends on 1)

The method of claim 1, wherein the step of generating an electromagnetic radiation signal with the transmitter further comprises the step of:
generating an infrared signal with the transmitter, the signal including a plurality of pulse pairs, each pair including a start pulse and a stop pulse, with the time interval between each start-and-stop pulse being proportional to a corresponding value in a predetermined key code sequence.

### Claim 3 (depends on 2)

The method of claim 2, wherein the step of generating an infrared signal with the transmitter further comprises the steps of:
obtaining a predetermined key code sequence from a code register;
generating an infrared signal; and
modulating the infrared signal to include a plurality of pulse pairs, each pair including a start pulse and a stop pulse, with the time interval between each start-and-stop pulse being proportional to a corresponding value in the predetermined key code sequence.

### Claim 4 (depends on 1)

The method of claim 1, wherein the steps of deriving the key code sequence, comparing the derived key code sequence to a predetermined lock code sequence and generating a valid signal further comprise the steps of:
using the time intervals in the received sequence of start-and-stop pulse pairs to start-and-stop an up-counter;
obtaining a predetermined lock code sequence from a code register;
summing each key code with each corresponding lock code; and
generating a valid signal if the vector sum of the codes is equal to zero.

### Claim 5

A secure remote control system, comprising:
a key transmitter for generating an electromagnetic radiation signal, the signal including a plurality of pulse pairs, each pair including a start pulse and a stop pulse, with the time interval between each start-and-stop pulse being proportional to a corresponding value in a predetermined key code sequence;
a lock receiver for detecting the electromagnetic signal, the receiver including:
means for deriving the key code sequence from the time intervals in the received sequence of start-and-stop pulse pairs;
means for comparing the derived key code sequence to a predetermined lock code sequence; and
means for generating a valid signal if each value in the derived key code sequence corresponds in a predetermined manner to each value in the lock code sequence wherein the means for generating a valid signal further comprises:
means for generating a valid signal if each value in the derived key code sequence is the complement of the corresponding value in the lock code sequence.

### Claim 6 (depends on 5)

The system of claim 5, wherein the key transmitter further comprises:
a key transmitter for generating an infrared signal, the signal including a plurality of pulse pairs, each pair including a start pulse and a stop pulse, with the time interval between each start-and-stop pulse being proportional to a corresponding value in a predetermined key code sequence.

### Claim 7 (depends on 6)

The system of claim 6, wherein the key transmitter further comprises:
a code register for storing a predetermined key code sequence; and
a modulator for modulating the infrared signal to include the plurality of pulse pairs.

### Claim 8 (depends on 5)

The system of claim 5, wherein the means for deriving the key code sequence further comprises:
an up-counter which is started and stopped by the time interval in each received start-and-stop pulse pair.

### Claim 9 (depends on 8)

The system of claim 8, wherein the means for comparing the derived key code sequence to a predetermined lock code sequence and the means for generating a valid signal further comprise:
a code register for storing a predetermined lock code sequence; and
a code comparison circuit for comparing each key code to each lock code and generating a valid signal if the vector sum of the codes is equal to zero.

### Claim 10 (depends on 5)

The system of claim 5, further comprising: reset means in the transmitter and the receiver by which a user can provide input to the transmitter to cause the transmitter to store a new key code sequence and the receiver to store a new lock code sequence.