Infrared control devices were developed several years ago for"cordless"control of domestic electrical equipment, in particular television receivers and video cassette recorders. The technology is widely used and well- established, and operates satisfactorily in enclosed situations such as a room in a house or hotel and where there is one controller and one controlled device. Such controllers and controlled devices are widely available in varying degrees of sophistication depending upon the degree and level of control required. However, as has been found in practice, problems start to arise if a plurality of controllers are used in conjunction with a plurality of controlled units, for example a television set, video cassette recorder and CD player, all used in the same room. Absent sophisticated encoding (or careful pointing of the controller, where the emitted signal beam

and/or the field of view of the controlled device is narrow), problems can arise in securing reliable control of a plurality of different devices.

This problem arises in particular in the case of remote controlled toys, for example vehicles which have their own on-board power supply and an infrared receiver and decoder arrangement which controls the movement of the vehicle in response to signals from a hand-held controller operated by the user. In order to guarantee that the vehicle can pick up the control signals, its receiver needs a very wide field of view, and conveniently the controller should also transmit over a relatively wide angle. While this does not matter in the play scenario of a single remote control vehicle and a single controller unit, problems immediately arise if two players wish to play together, for example competitively racing remote controlled vehicles round a predetermined series of obstacles laid out on a floor.

In the case of sophisticated remote control apparatus, for example radio controlled apparatus for operating model aircraft, is well-known to provide such apparatus with transmitters and receivers which may be set to operate over a number of pre-defined channels, for example ten to thirty channels, and if a number of enthusiasts meet together to operate simultaneously, they all agree to use different channels so that there is no interference, and inadvertent control signals sent by one party are not received by someone else's aircraft causing it to behave erratically or even to crash with damaging results. On the grounds of cost and convenience, this approach is inappropriate for infrared controlled toy vehicles.

While it would obviously be possible to produce infrared controlled toy vehicles with matching controllers, each

operating on a slightly different frequency, this increases costs, and with a practical number of frequencies still means that two independent purchasers could come together and find that the controller each had would control the vehicle owned by the other as well as their own, thus preventing independent control.

One way of overcoming the problem would appear to be simply to ensure that each transmitter/receiver pair was arranged to emit/receive and decode coded information identifying the transmission as coming from the correct transmitter unit. Although, in practice, this works after a fashion, problems arise when a transmitter is listening, but receives a signal which is composed of two superimposed signals, one transmitting one code block and the other transmitting another. This confuses the receiver and tends to result in failure of the receiver to recognise a coded transmission actually intended for it, resulting in loss of the desired control.

According to a first feature of the present invention, there is provided a multiple infrared control arrangement consisting of a plurality of infrared transmitters and a plurality of infrared reception and control units, wherein associated with each transmitter in each control unit is a broad band receiver adapted, on receipt of any coded infrared signal, to decode the signal, compare an identity code therein with an identity code pre-stored in the control unit and on coincidence, execute a control command transmitted by the transmitter.

More specifically, the invention provides a multiple infrared control arrangement comprising a plurality of transmitters and a plurality of receivers, each transmitter being constructed to transmit a signal including an identifying code as well as control data, and each receiver being adapted to decode the identifying

code and to actuate control functions correlated to the control data only when the correct code has been detected, wherein each transmitter is adapted to send signals in repeated blocks including the code and the control data followed by non-transmission for a period of time substantially larger than the time it takes to transmit the signal. Preferably the receivers include means for executing a control function in accordance with control data received only when two such signals are received immediately sequentially, i. e. within a preset short time period. The interval between transmission of one signal and the next or between the transmission of each pair of two signals and the next pair may be fixed or variable. In the first case, the transmitters should be synchronised and the times each transmits staggered with respect to the transmissions from the others. In the alternative, the transmitters may be set to repeat the signal or signal pair after a pseudo-random length of time, which may vary.

Operating in this way, no control function is effected by the receiving units until two blocks of control data has been successfully and immediately received and recognised as valid for that control unit. The relevant control function is then effected. In the case of the sending of pairs of signals at pseudo-random intervals, because the amount of time which elapses between one transmission of two identical signals and the next varies between the controllers, the various controllers do not operate in synchrony and sooner or later a clear patch arises during which each receiver receives two signals destined for it, whereafter the relevant control function may be undertaken. Although the time before this occurs will increase with an increasing number of controllers and receivers, it is never very long and in practice usually imperceptible. Using standard transmission technology and a transmission frequency of e. g. 38 kHz (a commonly

adopted standard), the length of time for transmission of each signal may be, e. g. 5 to 15 milliseconds, followed by a spacing of 50 to 250 milliseconds before the next transmission of a pair of signals. If a higher transmission frequency is used, then times shorten correspondingly. In practice, if several people are controlling a number of independent devices, all using infrared transmitters, all operating on the same frequency, but with signals transmitted in this way, some of the receivers will react sometimes a little slower than others, but not to an extent perceptible by the individual users. For large numbers of users, it is desirable to use shorter transmission times and longer spacings to avoid risk of any interference.

In the mode of operation indicated above and requiring synchrony, the transmitters are preferably so constructed that on placing two or more of them in close proximity, each will detect the presence of the others and synchronise transmission allocations to ensure that no two transmitters transmit the signal or pair of signals at the same time as any other. This may be achieved using direct electrical coupling, e. g. by providing each transmitter unit with a conductive plug and mating socket so that any number may be"chained"together, or by e. g. inductive coupling.

In an alternative approach, each transmitter unit may be associated with a receiver unit adapted to receive a start signal from a first transmitter unit, and set its associated transmitter to transmit at a given first time interval from the first transmitter; the transmitter unit so set may then transmit to a second such transmitter/receiver unit, and so on, or the first transmitter unit may be programmed to set a second unit to transmit at a first given delay, a third unit at a second (different) delay, and so on.

As indicated above, each receiver is arranged to decode an identifying code and check if it matches a stored code, a match then enabling the control data to be effective. In order to do this, the receiver must include means for storing an identity code and comparing it with a received identity code. Preferably, that storage means may be programmed by the transmitter, e. g. on the actuation of an enabling circuit by the user.

Thus a set of initially identical receiver units may be sequentially provided with a set of different identity codes, whereafter the multiple control arrangement will function.

Alternatively, but less preferably, each receiver may include a preset code and the transmitter may be adjusted e. g. to scan through the possible codes until a match is found, and the fact of a match demonstrated by some suitable signal from the receiver such as illumination of an LED or actuation of an acoustic transducer.

Such learning modes may be controlled by a user, e. g. using"learn"buttons on transmitter or receiver units, or may be initiated automatically on a transmitter or receiver unit being switched on. If desired, the identifying code may be selected by a user using a suitable input system e. g. a DIP switch array or the sequential actuation of a sequence of push button depressions, this last being useful when the multiple infrared control arrangement is embodied in a system which requires a push button input for normal operation.

The multiple infrared control arrangement of the present invention is useful in a wide variety of areas of application, including multiple remote controlled toy vehicle sets, warehouse robot pickers, and production line process control. The controlled units do not all have to be of the same type: for example, some may be

wheeled vehicles and others controllable obstacles such as drawbridges or swing bridges, level crossings or the like., similarly, the transmitters do not need to be of the same type-some could be handhold control units and some in the form of a PC, games console or the like fitted with a suitable IR output card and suitably programmed.

The invention is further explained with reference to the attached drawings which show diagrammatically how the invention may be applied to a toy vehicle product. In the drawings: Figure 1 is a diagrammatic illustration of a toy remote control racing car set.

Referring to the drawing, Figure 1 shows a set of six toy racing cars 1 to 6 which are coordinated with a set of six infrared control units 11 to 16. Each control unit contains an infrared transmitting device of known type, operated on battery power by a cell or cells located in a casing of the control unit and which is adapted to emit control signals which, when decoded, can cause the corresponding cars to go faster or slower and steer to the left or to the right. Such controllers and the manipulatable buttons, joystick or other device for operating them are well-known and the details do not need to be described further here. However, the electronic control of the infrared emitting diode which sends the signal from transmitter to receiver is modified in two ways: First, each controller is adapted to transmit information using short period signals, the first portion of each of which contains a code. The code may be very simple and consist of a binary number selected from the range 0000 to 1111. Each transmitter unit has a set of four two-

position switches 21-26, conveniently in the form of a DIP switch block, enabling the switch position to be set to correspond to one of the sixteen binary numbers which can be represented by four digits. The cars likewise have similar switch blocks 31-36 so that each car can be coordinated with one controller and vice versa.

Each of the transmitters is arranged to transmit coded information consisting of the code identifier block followed by a control data block, twice, in the form of two successive transmitted blocks of information.

Thereafter, transmission is inhibited for a number of time units being a multiple, preferably at least six times, the time unit required for transmitting one block.

This way, even if all six transmitters are transmitting at the same time and on the same frequency, each is silent for most of the time and sooner or later will transmit its two blocks of information at a time when none of the other five transmitters are transmitting.

This may be achieved by the method described above. Once a two blocks signal has been picked up by its corresponding receiver in the corresponding vehicle, and accepted as valid because of their being both the same on the one hand and possessing the right code on the other, the control signal which follows as part of the block can then be actuated, e. g. to speed up or slow down a vehicle or to steer it to the left or the right. The power for the receiver in each of cars 1 to 6 and for making the cars go is provided by a conventional battery in a suitable battery compartment in each car.

A variety of game scenarios can be envisaged, of which the following are illustrative.

1. Operational Instructions For a Single Remote Control Unit Controlling a Single Car

1. Press a learn key on the control unit. An LED will flash on the remote control unit at a regular rate. Place the car to be used on the ground. Direct the remote control head towards the car's receiving head. When the car receives the learn command, the small LED on the car will flash.

2. Press any combination of keys other than the learn key to set a user defined identification setting. When the car has received a valid transmission, the LED on the car will turn on for approximately 1 second.

3. The user is now ready to control the car.

4. If any car does not respond to the learn mode, then the car may be out of range of the remote controller.

2. Operational Instructions for a Single Remote Control Unit Controlling Multiple Cars 1. Press the learn key on the control unit. An LED will flash on the remote control at a regular rate. Place the cars to be used in a cluster on the ground. Direct the remote control head towards the cars. When the cars receive the learn command, a small LED in each will flash.

2. Press any combination of keys other than the learn key to set a user defined identification setting. When the cars have received a valid transmission, their LEDs will turn on for approximately 1 second.

3. The user is now ready to control the cars with a single control unit.

4. If any car does not respond to the learn mode, then the car may be out of range of the remote control unit.

3. Operational Instructions for Several Remote Control Units, Each Individually Controlling One of Several 1. Each remote control unit is required to set the ID on its designated car by following the single remote and single car learn sequence.

2. The remote control units will be connected together at the start of play.

3. The learn key is now pressed on one of the remote control units to synchronise the set of remote control units that will take part in the multiple remote and multiple car game play.

In all of these cases, the remote control may have 8 individual keys (e. g. to correspond to the commands left, right, forward, reverse, stop, learn, spin and aux).

When applied to a toy car with rear wheel drive control, the car response may depend on the keys pressed as shown in the following table:

KEYS DEPRESSED ACTION FORWARD FORWARD FORWARD + RIGHT SHARP RIGHT CLOCKWISE FORWARD + LEFT SHARP LEFT ANTI-CLOCKWISE REVERSE REVERSE REVERSE + RIGHT SHARP RIGHT ANTI-CLOCKWISE REVERSE + LEFT SHARP LEFT CLOCKWISE SPIN + RIGHT SPIN CLOCKWISE SPIN + LEFT SPIN ANTI-CLOCKWISE STOP STOP (This may not be required) LEARN LEARN USER ID AUX LOGICAL I/O for sound trigger, etc.

If desired, the code learning feature identified above may be made use of during an actual play activity. Thus, the code in any one of a plurality of vehicles may be changed in mid play, e. g. to pass control of a vehicle from one transmitter unit to another, for example reflecting a change of vehicle in a"relay race"or the capture of a vehicle by an"enemy"in a more military form of game.