This invention relates to improvements to switching systems and in particular to a method and apparatus for switching. Background Art

Many current switching devices are characterised by their reliance on mechanical components such as in toggle switches, knife switches, plunger switches and rotary switches which may be either operated directly or remotely by secondary means. Other switching devices comprise semiconductor devices such as transistors. Semiconductor switches are commonly used in electronic equipment. These switches are also limited by the speed of operation, the size, their relative complexity, and/or their difficulty and expense to manufacture for specific purposes. The speed of operation of these switches particularly in data processing applications such as in computers limits the speed of operation of a computer. Components of computers have been characterised by a reliance on direct current transistor type switches in a variety of forms resulting in limitations on computational speed and further restricting computer development by problems arising directly from the heat output from such devices and restricting further miniaturisation imposed by the physical requirements of such devices. Such computer systems are additionally limited in their development by their requirement of one or more dedicated timing devices such as the clock components of contemporary computers which provided regular pulsed input for the control of the operating sequence of the systems. The use of such clocks introduces additional complexity to the system in the form of added circuitry or dedicated components with the sum of the above severely limiting advances in the computational speed of computer systems. Summary of the Invention

The present invention aims to provide switching

methods and systems which overcome or alleviate the aforementioned disadvantages of the prior art or at least provide an alternative to the prior art switching methods and systems. In a particular aspect, the present invention aims to provide switching methods and systems which have enhanced capabilities in their speed of operation. Other objects and advantages of the invention will become apparent from the following description.

The present invention thus provides in a first aspect a switching system including first signal emitting means for emitting a first signal, second signal emitting means for selectively emitting a second signal, and signal detecting means for detecting signals emitted by said first and second signal emitting means, said signal detecting means providing variations in output and thereby a switching function in accordance with said signals selectively emitted by said second signal emitting means.

In one form, the second signal emitting means is adapted to selectively emit a signal which cancels the signal emitted by said first signal emitting means as received or detected by said detecting means. For this purpose, the signal emitted by the second signal emitter is at the same or substantially the same frequency or range of frequencies as the signal emitted by the first signal emitting means but 180 degrees out of phase with that signal.

In a further form, the signal emitted by the second signal emitting means adds to the signal emitted by the first signal emitting means as received or detected by the detecting means whereby the detecting means detects variations in amplitude of signal received in accordance with the signal emitted by the second signal emitting means. In this form therefore, the signal emitted by the second signal emitting means may be in phase with that emitted by the first signal emitting means. This variation in detected amplitude may also be use to provide a switching function.

The first signal emitting means may comprise one

or more signal emitting devices adapted to emit signals at discrete frequencies in the electromagnetic spectrum.

The second signal emitting means may also comprises one or more signal emitting devices adapted to emit signals at discrete frequencies in the electromagnetic spectrum matched to the frequencies of respective signals emitted by first signal emitting devices.

The signal detecting means may comprise one or more signal detecting means for detecting the presence or of the signal or signals emitted by the first and second signal emitting device or devices.

As stated above, switching of the signal emitting devices may be accomplished by the cancellation or otherwise of the signal or signals emitted by the first emitting device or devices by the signal or signals emitted by the corresponding second emitting device or devices.

Alternatively, the signal detecting device or devices may be adapted to register in variations in amplitude of the signals emitted. In this instance, switching is accomplished by either the cancellation or amplification of the signals emitted by the first emitting device or devices at the point of registration of the detecting device or devices.

In an application to data processing for example in computers, one or more of the signals emitted may be employed as a functional clock for the control of the operating sequence of the equipment allowing the use of a clock speed equal to or a multiple or division of the frequency of that signal or signals. The signal emitting means may be arranged to emit signals having a frequency in the visible light spectrum in which case the signal detecting means comprises a light detector or detectors. Alternatively, the signal emitting means may be arranged to emit signals of other frequencies in the electromagnetic spectrum.

Where the light emitting means emit light signals, the emitting means and detecting means are arranged in line of sight of each whereby the signals may

be transmitted or received.

The signal emitters and signal detectors however may be any devices known in the art including semiconductor devices. In a further aspect, the present invention provides a method of switching, said method including the steps of emitting a first signal, emitting a second signal, detecting said first and second signals to provide a switching output in accordance with the frequency and phase of said first and second signals.

The second signal may be selectively emitted whereby to provide selective variation in the switching output. The second signal may be emitted so as to be 180 degrees out of phase with the first signal whereby when emitted, it effectively cancels the first signal. The first and second signals may be at substantially the same frequency or range of frequencies.

Alternatively, the second signal may be in phase with the first signal to add to the amplitude of the signal detected.

Brief Description of the Drawings

In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein :-

Fig. 1 is a block diagram of a switching system according to the present invention; and

Figs. 2 to 5 illustrate schematically the operation of the switching system according to the present invention.

Detailed Description of the Embodiment

Referring to the drawings and firstly to Fig. 1, there is illustrated a switching system 10 according to an embodiment of the present invention including a first signal emitter 11 for emitting a signal at a specific frequency or range of frequencies, and a detector 12 for detecting the signal emitted by the first signal emitter 11.

The system 10 further includes a second signal emitter 13 which is adapted to emit a signal at the same specific frequency or range of frequencies as the first signal emitter 11. The signals emitted by the second signal emitter 13 however are 180 degrees out of phase with the signals emitted by the first signal emitter 11. The signal detector 12 is also capable of detecting the signal emitted by the second signal emitter 13.

In operation and assuming that the signal emitter 11 emits a signal at a certain frequency, that signal is detected by the detector 12 which is excited and provides an output upon detecting that signal. If the second signal emitter 13 however also emits a signal which is at the same frequency as that emitted by the first signal emitter 11 but 180 degrees out of phase, that signal is also detected by the detector 12. As however the respective signals emitted by the first and second signal emitters are substantially the same but 180 degrees out of phase, the signal emitted by the second emitter will in effect cancel the signal emitted by the first signal emitter 11 thus providing no output from or excitation of the detector 12. Thus the excitation or otherwise of the detector 12 provides a switching effect or signal which can be used in many different switching applications. In one such application, the signal emitters 11 and 13 may be laser emitters and the detector 12 comprises a light detector which is either excited when for example a light signal is received from the emitter 11 but which is not excited if it receives from the emitter 13 a signal of the same frequency but of opposite phase. The output of the detector 12 thus serves to provide a switching function.

Figs. 2 to 5 illustrate schematically the principles of operation of the switching system 10 of the invention described above. In Fig. 2, a primary signal emitter 11 emits a primary signal 14 which is continuously detected at the sensor or detector 12, the signal in this example being in the form of a sine wave. This detected

signal may be used as a functional clock for cycling the operating sequence of data processing equipment at or at multiples or divisions of the frequency of the signal.

If as shown in Fig. 3, a secondary emitter 13 emits a secondary signal 15 which is of the same frequency as the primary signal 14 but 180 degrees out of phase, it will continuously cancel the signal 14 emitted by the primary emitter 11 as detected by the detector 12.

If as shown in Fig. 3 and 4, the secondary signal 15 is interrupted and thus only intermittently cancels the primary signal 14, the detector 11 will provide an output or will change state intermittently as governed by the interruption provided by the secondary signal 15. This therefore provides a switching function. Whilst the system of the invention is primarily used in a configuration where the signal emitted by the secondary emitter 13 cancels the signal emitted by the primary emitter 11 to thereby control the state of the detector, the detector 12 may also be selected to provide various degrees of excitement depending upon the amplitude of the signal which it receives. Switching in this instance is accomplished by the variation in amplitude of the signal received by the detector. In this form, the signal or signals emitted by the secondary emitter 13 may be in phase with the signal emitted by the primary emitter 12 so as to add to the amplitude of that signal as detected by the detector.

Of course the output provided by the detector may vary in accordance with the application. For example no output may be provided where the signal emitted by the second emitter cancels the signal emitted by the first emitter whilst the detector may provide a high output where the signal of the first emitter is not cancelled. Alternatively, the detector may provide a high output where the signals cancel and a low output where the first signal is not cancelled.

Whilst the above has been given by way of illustrative embodiment of the invention, all such

modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein defined the appended claims.