Data transmission system

Abstract: In a digital data transmission and reception system, data to be transmitted is converted into a series of data pulses (2) representing bits. Regular timing pulses (1) with a fixed period (3) are transmitted with each data pulse (2) between successive synchronous timing pulses (1). The bits "0" and "1" are represented by the time duration between a data pulse and a preceding or succeeding timing pulse.

Description: FIELD OF THE INVENTION The present invention relates to a method of and system for data transmission and reception, particularly one suitable for remote control using infrared or light radiation. BACKGROUND OF THE INVENTION A known remote control system, such as one used for home appliances, and described hereinafter suffers from various disadvantages. Principally, the system is vulnerable to extraneous affects or noise. SUMMARY OF THE INVENTION An object of the invention is to provide an improved data transmission and reception system and method. According to one aspect of the invention, there is provided a method of digital data transmission and reception which comprises converting and transmitting information as a series of data pulses representing one bit each, providing a series of successive synchronous timing pulses with a fixed period, interposing one single data pulse between successive timing pulses to represent bits depending on the duration between each of the data pulses and the preceding or succeeding timing pulse, the duration of each timing pulse being different to the duration of each data pulse, receiving the timing and data pulses, decoding and extracting the information represented by the data pulses and determining whether more than one data pulse occurs between a pair of successive timing pulses to inhibit noise. The invention also provides a digital data transmission and reception system comprising a transmitter and a receiver, said transmitter comprising means for converting and transmitting information as a series of data pulses representing one bit each and means for generating a series of successive synchronous timing pulses with a fixed period for transmission with one single data pulse being transmitted between successive synchronous timing pulses, each of the bits being represented by the time duration between one of the data pulses and a preceding synchronous timing pulse or a succeeding synchronous timing pulse and the pulsewidth of the data pulses differing from the pulsewidth of the synchronous timing pulses, said receiver serving to receive the timing and data pulses and employing decoding means for extracting the information represented by the data pulses and the system further comprising noise inhibition means which functions by determining whether more than one data pulse occurs between a pair of successive timing pulses. Conveniently, the signals are transmitted as data words each formed from seven successive timing pulses and six data pulses. With the arrangement in accordance with the invention, the timing length for each word can be fixed and decoding of data is therefore facilitated. Extraneous influences such as noise can create additional pulses at random times but the presence of such noise pulses can be easily detected by the noise inhibition means by counting and determining whether more than one data pulse occurs between a pair of successive timing pulses. Any noise can thus be suppressed at the receiving end and erroneous operations can be avoided. The invention may be understood more readily and various other features of the invention may become apparently from consideration of the following descriptions. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:- Fig. 1 is a block diagram showing a prior art system; Fig. 2 is a waveform diagram which depicts signals representing the bits "0" and "1" according to the system of Fig. 1; Fig. 3 is a waveform diagram showing an example of a transmitted code word composed of 6 bits according to the system of Fig. 1; Fig. 4 is a waveform diagram which depicts one deleterious effect of noise on the signals in the system of Fig. 1; Fig. 5 is a block diagram showing a system constructed in accordance with the invention; Fig. 6 is a waveform diagram which depicts signals representing the bits "0" and "1" according to the system of Fig. 5; Fig. 7 is a waveform diagram showing an example of a transmitted code word composed of 6 bits according to the system of Fig. 5; Fig. 8 is a waveform diagram which depicts the typical effect of noise on the signals in the system of Fig.5; and Fig. 9 is a block diagram showing an example of remote control system incorporating the data transmission and reception system of Fig. 5. Fig. 1 shows the main components of a data transmission and reception system for use in the control of home appliances such as a T.V., V.C.R., air conditioner and the like. The system employs a transmitter 31 and a radiation emitter 33 such as an LED or equivalent infrared device provided in a conveniently portable remote controller. A detector 34 sensitive to the radiation emanating from the transmitter 33 co-operates with a receiver 32. Normally, the detector 34 and the receiver 32 would be provided on or in the appliance. Information representing a command would be inputted to the controller via a keyboard or pad. This information is encoded and modulated in the transmitter 31 and converted by the emitter 33 into equivalent signals in the form of radiation, e.g. light propagated through the atmosphere to the detector 34. The detector 34 converts the received signals back into electrical signals which are demodulated and decoded and used to actuate some function of the appliance. The bits "0" and "1" are signified in this system by the duration between successive pulses (radiation or electrical) as depicted in Figure 2. Thus, a short time interval 41 between the rising edge of a first pulse and the rising edge of a second succeeding pulse denotes "0" while a longer time interval 42 between the respective leading edges denotes "1". A group of the bits "0" and "1" such as six bits forms a word as shown in Fig.3. Each word may define one instruction or command. In this known system, the time occupied by each word varies depending on the number of "0"'s and "1"'s in its make up and the duration of each word is hence unknown by the receiver until the transmission of the word has ended. This uncertainty creates difficulties in decoding and the system is vulnerable to noise, particularly from fluorescent lighting. For example, when two pulses shown at the top of the Fig.4 define the bit "1", the occurrence of a stray pulse 61 caused by noise between the successive pulses will alter the information and cause the receiver to interpret the signal as "00" rather than "1". DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the data transmission and reception system in accordance with the invention will now be described with reference to Fig. 5 which uses the same reference numerals as in Fig. 1 to denote identical or similar components. The system of Fig. 5 is shown to be identical to the system of Fig. 1 but the system operates in a somewhat different manner as will now be explained. Essentially, in the system of Fig. 5, the signals transmitted and received are composed of timing pulses and data pulses. As shown in Fig. 6, the data pulses denoted as 2 are inserted between successive synchronous pulses 1 having a fixed period 3 therebetween. The time intervals 4 and 6 between the rising edges of the data pulses 2 and the rising edge of the immediately preceding synchronous timing pulse 1 or the time intervals 5 and 7 which occur between the rising edges of the data pulses 2 and the rising edges of the immediately succeeding timing pulses 1 define the bits "0" and "1". In a practical example, each timing pulse 1 has a duration of 0.25 ms and the period 3 between succeeding synchronous timing pulses 1 is 3 ms. The time duration 4 set for the bits "0" is 1 ms and the time duration 6 set for the bit "1" is 2 ms. These times can, of course, be altered. The full data configuration can be as shown in Fig. 7. Each word is again composed of six bits but now each word also contains 7 synchronous timing pulses with the data pulses occurring between pairs of timing pulses at intervals depending on whether they signify a "0" or "1". In the example of Fig. 7, the cord word transmitted is "011001". The time duration for each code word in the system is 18.25 ms (=3 ms x 6 + 0.25 ms) irrespective of the number of "0"s or "1"s. Should a noise pulse 71 occur as shown in Fig. 8, two pulses will be detected during the fixed period between successive synchronous timing pulses 1 instead of one. It is therefore readily apparent that a fault has occurred and inhibition circuitry designed to count the number of pulses between a pair of timing pulses 1 can ensure that misinterpretation at the receiver will not take place. Fig. 9 shows an example of a digital remote control system incorporating the system of Fig. 5. As illustrated, there is provided, at the transmitting end, i.e. a remote controller, a keyboard or key matrix 10 for manually inputting the instructions for the control of some electrical appliance. When a key in the key matrix 10 is depressed, a key input read circuit 11 detects the data represented by the key thus depressed and supplies this data to a code modulation circuit 12. Control signals for the code modulation circuit 12 are supplied by a timing generator 13 receiving timing pulses from a clock pulse generator or oscillator 14. In the code modulation circuit 12, a data code corresponding to the inputted data is produced and converted into series of data pulses each positioned between successive synchronous timing pulses as described previously. The output of the code modulation circuit 12 is applied to a transistor of a driver circuit 15, thereby to drive a light-emitting diode 16 to cause the latter to output a modulated light signal. At the receiving end, i.e. the operative part of the electrical appliance to be controlled by the remote controller, the transmitted light signal is received by a photodiode 17, the output of which is applied through a preamplifier to a remote control signal demodulation circuit 19. The signal thus applied is demodulated and used for the control of the appliance in question. In contrast to the known system, the system described in connection with Figs. 5 and 9, has a fixed period defining each word and extraneous pulses caused by noise can be easily detected and precluded from the control function. Data and timing pulses are further distinguished by their duration. The synchronous timing pulses and the data pulses may to be transmitted after being modulated at a specific frequency, so that the necessary frequence band width can be quite low. If desired, a lead pulse having a larger pulsewidth may be placed in front of the code for the data being transmitted to assist the detector. Although the system described utilises transmitted radiation such as light in free air, the invention is also applicable in a system where radiation or electrical pulses are conveyed by a cable, an electrical conductor, a light guide or otherwise.

Claims: A digital data transmission and reception system comprising a transmitter and a receiver, said transmitter comprising means (31, 33, 11, 12, 15, 15) for converting and transmitting information as a series of data pulses (2) representing one bit each and means (13, 14) for generating a series of successive synchronous timing pulses (1) with a fixed period for transmission with one single data pulse (2) being transmitted between successive synchronous timing pulses, each of the bits being represented by the time duration between one of the data pulses and a preceding synchronous timing pulse or a succeeding synchronous timing pulse and the pulsewidth of the data pulses (2) differing from the pulsewidth of the synchronous timing pulses (1), said receiver (34, 32, 18, 19) serving to receive the timing and data pulses and employing decoding means for extracting the information represented by the data pulses and the system further comprising noise inhibition means which functions by determining whether more than one data pulse occurs between a pair of successive timing pulses. A system according to claim 1, wherein the time duration between each of the data pulses (2) and the immediately preceding synchronous timing pulse (1) has either a first or a second value to represent the bit "0" or "1". A system according to claim 1 or 2, wherein data words are each formed from seven successive timing pulses and six data pulses. A method of digital data transmission and reception which comprises converting and transmitting information as a series of data pulses (2) representing one bit each, providing a series of successive synchronous timing pulses (1) with a fixed period (3), interposing one single data pulse between successive timing pulses to represent bits depending on the duration (4, 5, 6, 7) between each of the data pulses (2) and the preceding or succeeding timing pulse (1), the duration of each timing pulse (1) being different to the duration of each data pulse, receiving the timing and data pulses, decoding and extracting the information represented by the data pulses and determining whether more that one data pulse occurs between a pair of successive timing pulses to inhibit noise. A method according to claim 4, wherein data words are each formed from seven successive timing pulses and six data pulses. A digital remote control system employing a system according to any one of claims 1 to 3, wherein the transmitter is in the form of a remote controller usable to control equipment incorporating the receiver and the information represented by the data pulses serves as a control instruction for controlling the equipment.

Inventors: HONGO KATSUNOBU C O MITSUBISHI, KOBAYASHI HIROSHI C O MITSUBIS, SUDA SHINJI C O MITSUBISHI DEN, HONGO, KATSUNOBU C/O MITSUBISHI DENKI, KOBAYASHI, HIROSHI C/O MITSUBISHI DENKI, SUDA, SHINJI C/O MITSUBISHI DENKI
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1987
Main classification: G08C19
IPC codes: H03M5, H04L25, G08C19, H04L7