MOBILE COMMUNICATIONS EQUIPMENT

WORLD INTELLECTUAL PROPERTY ORGANIZATION International Bureau PCI' INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREAIT (PCn f- (51) International Patent Oassification 5 : (11) International Publication Number: A1 H04Q 7/04, H04M 1172 H04B 7/26 PCTI A U90100020 (21) International Application Number: (22) International Filing Date: (30) Priority data: PJ 2381 (43) International Publication Date: 23 January 1990 (23.01.90) 23 January 1989 (23.01.89) WO 90/08447 26 July 1990 (26.07.90) (81) Designated States: AT (European patent), AU, BE (European patent), CA, CH (European patent), DE (European patent), DK (European patent), ES (European patent), FR (European patent), GB (European patent), IT (European patent), JP, KR, LU (European patent). NL (European patent), NO, SE (European patent), US. AU (71) Applicant (for all designated States except US): SUPERIOR ELECTRONIC DEVELOPMENTS PTY. LTD. [AUI AU]; 131 Station Street, Fairfield, VIC 3078 (AU). Published With international search report. (72) Inventor; and (75) Inventor!Applicant (for US onM : TIRKEL, Anatol, Zygmunt [AUI AU]; 21 Walstab Street, East Brighton, VIC 3187 (AU). (74) Agents: PRYOR, Geoffrey, Charles et a!.; Davies & Collison, I Little Collins Street, Melb.ourne, VIC 3000 (AU). (54) Title: MOBILE COMMUNICATIONS EQUIPMENT 15 (57) Abstract Mobile telecommunications equipment comprising a vehicle mounted mobile base unit (2) and a number of portable units (1) which may comprise portable telephones. The first and second units (2) are interconnected by a communication link (4), the units including a microprocessor (8) which senses characteristics of the communication link (4), the equipment further including feedback and control means (5, 8) for adaptive control of the link in accordance with the communications environment. 7 T/R SWITCH 6 5 TRANSMITTER RECEIVER 8 MICROPROCESSOR AND INPUT I OUTPUT CONTROL ELEMENTS DIGITISER 10 9 AUDIO OUT D/A CONVERTER 94 11 FOR THE PURPOSES OF INFORMATION ONLY Codes used to identify States party to the PCf on the front pages of pamphlets publishing international applications under the PCf. AT AU Austria Ausualia Fl B8 Barbados FR BE BcJpJm Budina Fasso Bqaria Benin GA GB HU IT JP KP BF BG BJ BR CA CF CG CH CM DE OK Brazil Canada Central African Republic: Congo Switzerland Cameroon Germany, Federal Republic: of Denmark - ｾ＠ KR U LK ill Me Spain rmland MG ML France Gabon United Kingdom Hungary Italy Japan Democratic People's Republic: of Korea Republic: of Korea Liechtenstein Sri Lanka Luxembourg Monaco MR rrNI NL NO RO Sl SE Sol SJ 11) TG US Madagascar Mali Mauritania Malawi Netherlands Norway Romania Sudan Sweden Senegal SOviet Unian Chad Togo United States of America PCfI AU90/00020 WO 90/08447 - 1 - MOBILE COMMUNICATIONS EQUIPMENT The present invention relates to mobile communications equipment and finds particular application in systems incorporating mobile or portable radio telephone units. 'Mobile communications equipment is known which comprises a telephone switching system or .. network, for instance the public switched telephone network, by means of which mobile or portable radio telephone ,uni ts can communica teo. Each uni t can usually communicate, via the switching system or network, either with another mobile unit or with a fixed conventional telephone unit such as a wired subscriber's telephone. To establish communication between the mobile unit and the network, a radio or similar link is generally provided between each mobile unit and the switching system or network. A potential problem arises however in that if two or more mobile units are operative within communication range of each other, interference or ; I SUBSTITUTE SHEET 'tl PCf/ AU90/00020 W090/08447 - 2 - possibly -eavesdropping- can occur. This problem has been overcome in particular environments in the past by various means. For instance, in cellular telephone systems, an area served by a telephone network is divided into cells and a fixed network transceiver is allotted to each cell. Mobile units within a cell access the network by communicating with the fixed transceiver by means of allotted frequency channels. Allotment of the channels is centrally controlled by the network. The above solution is acceptable within the constraints of a cellular telephone system. Channel allotment within each cell, and the size of the cells, can be tailored to local conditions. Hence in crowded geographical areas, each cell will be relatively small and, if possible, will have a high number of channels allocated to it. Conversely, in a sparsely populated area, each cell will generally be substantially larger. However, there are communication environments in which such central control of channel allotment , and the predetermined manner in which the cells are designed, are inappropriate. As well as interference between mobile units, other problems have been recognised such as local variations in transmission conditions. Indeed, communications equipment may be required to operate in a communication environment which can be rendered hostile by any of the following: i) initial interference between neighbouring RF links; ii) interference from external sources; iii) interference due to multipath transmission (which can occur for instance due to I SUBSTITUTE SHEET PCfI AU90/00020 W090/08447 - 3 - reflections in the path of the RF link); iv) signal fading (which can occur for instance due to obstructions moving into the path of the RF link). Various solutions have been put forward, including the use of directional antennae or leaky transmission lines as variations of the transmission link. However, such solutions are limited to use in a relatively ｾｯｮｴｲｬ･､＠ or predictable ･ｾｶｩｲｯｮｭｴＬ＠ such as within a building or for generaliy small scale communication systems. A further constraint on equipment employing mobile or portable units is that they may have to conform to stringent size, weight, power consumption and cost constraints, as well as offering the user a degree of conununications privacy. An object of the present invention is to provide mobile communications equipment in which the above problems are ameliorated, and which can be designed to meet the above constraint. According to a first aspect of the present invention there is provided .mobile communications equipment comprising a first, mobile unit incorporating transceiving means, and a second unit incorporating transceiving means and connection means for connecting the second unit to a telephone switching system or network, the ｴｲ｡ｮｳ｣･Ｚｾｩ［＠ ｾ･｡ｮｳ＠ of the first and second units being adapted for establishing a communication link between them, wherein either the first, mobile unit or the second unit further incorporates a sensor for sensing characteristics of the communication link, and the equipment further comprises feedback and control means for controlling aspects of said link in I SUBSTITUTE SH£ET PCII AU90/00020 WQ90/08447 - 4 response to the sensed characteristics, such that the link is adaptive in accordance with its communications environment. The link may comprise a radio communications link. Preferably the characteristics sensed by the sensor include characteristics of the link after it has been established, such that the link is dynamically adaptive in accordance with its communications environment. The characteristics sensed by the sensor may advantageously include the level of interference associated with the link and/or the signal power being received over the link. Such communications equipment can be used in a variety of environments and in particular it can be used ｷｨ･ｲｾ＠ the environment relevant to the communication link is likely to vary. Thus it is particularly useful where the second unit may be connected to any of a variety of points in a geographically dispersed telephone switching system or network, such as the public switched telephone network, since the equipment can automatically and immediately provide an acceptable quality of communication link, within reasonable limits, regardless of the local conditions under which the link must be established. Additionally, it is particularly useful where the number and mobile nature of the units in a mobile communications arrangement means that the number of communication links established in a small area can vary substantially. For instance, in any area which attracts a crowd it is possible that a large number of mobile units will be brought together SUBSTITUTE SH£ET j ! • PCfI AU90/00020 W090/08447 - 5 - and operated at the same time and in the same locality. It is not necessarily convenient or possible to predict where such a crowd might gather and then to provide equipment according to a centrally organised system of known type, that will give acceptable facilities under widely varying conditions. However, equipment according to embodiments of the present invention can detect the effect of a change in local occupancy and adapt its manner of operation to avoid ｩｮｴ･ｲｦｾ｣＠ between competing communication links. Preferably the communication link established between the transceiving means of the first and second units is coded according to a spread spectrum technique (SST) wherein transll:ission is based on a broadband frequency regime. Instead of employing tightly controlled, narrow frequency band carriers to provide separate channels for neighbouring communication links, as is known for instance in cellular telephone systems, each channel is differentiated by modulation of the carrier frequency according to a predetermined code. For instance, the modulation might comprise frequency hopping between two or more specified frequencies. Such techniques have an inherent advantage in that low signal power at any single frequency lIlay be used, which sigr.ificantly reduces interference with or by other equipment. Additionally, the nuffiter of channels available, defined by.unique and distinguishable codes, is considerably greater than when channels are defined by narrow frequency bands. Clearly, embodiments of the invention may include arrangements wherein the first aDd second units are both mobile and indeed the adaptive quality I- SUBSTITUTE SHf.ET perlAU90/00020 W090/08447 - 6 - of such embodiments is then of enhanced importance. Both the first and second units may include a sensor for sensing characteristics of the communication link established between them, linked to the feedback and control means. A particular aspect of an SST communication link which may be controlled by the control means is the SST code assigned to it. In the case where two established communication links move closer to one another as a result of movement of at least one of the associated units, and begin to interfere because their allocated codes are not sufficiently distinguishable, the control means may instigate a -back-off- procedure whereby the allocated codes are changed so as to eradicate the interference. Communications equipment according to embodiments of the present invention will now be described, by way of example only, with reference to the accompanying Figures in which: Figure 1 shows a schematic diagram of communications equipment according to an embodiment of the present invention, for use with a cellular telephone system; Figure 2 shows a block diagram of elements of a transceiving unit for use in the equipment of Fig-ure Ii Figure 3 shews in-more detail selected elements of the unit shown in Figure 2, including transmitting, receiving and correlating means; Figure 4 shows a block diagram of steps performed under the control of a microprocessor in converting an audio voice signal for supply to the transmitting means of Figure 3; Figure 5 shows in greater detail a switch " SUBSTITUTE SH£ET j PCfI AU90/00020 W090/08447 - 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 shown in block form in Figure 3; Figure 6 shows in greater detail a single side band upconverter shown in block form in Figure 3; Figure 7 shows in greater detail an oscillator and audio input shown in Figure 3; Figure 8 shows schematically the control process of a microprocessor shown in block form in Figure 2; Figure 9 shows frequency responses of components of the oscillator and audio input shown in Figure 7; Figure 10 shows a modified system of the invention; Figure 11 illustrates in more detail some of the receiver components of Figure 10; and Figure 12 shows still further detail of some of the carrier detection and AGe components of Figure 11. 15 16 17 18 19 20 21 22 23 24 25 Referring to Figure 1, a particular form of the communications equipment may comprise two mobile transceiving, units, one of which is a base unit 1 having coupling means 3 for direct or indirect connection to a telephone switching system or network, and the other of which is a remote unit 2 carried by a user. The coupling means 3 may for instance comprise an audio port for communication via a cellular telephone with a fixed base station of a cellular telephone network, or a plug for direct connection into,. a PSTN. 26 27 28 29 30 31 32 33 34 35 36 37 Communication between the two mobile units 1, 2 takes place over a radio frequency (RF) communication link 4 established under the control of either mobile unit 1, 2 and monitored by both units 1, 2. The RF link 4 exploits SST signalling and data is sent in packet format, time division multiplexed, with identifying address information to alert the remote unit 2. In a particular embodiment, the overall manner in which the communications equipment may be used is as a "pocket radio" link for application as a 38 SUBSTITUTE SH£ET PCfI AU90/00020 W090/08447 - 8 - remote extension of a vehicle-based cellular telephone. The base unit 1 receives the audio output of the cellular telephone and converts it for retransmission by means of the RF link • to the remote unit 2 which may be a selected one of a plurality of remote units 2. The RF link 4 can be described as a half duplex, spread spectrum link which relies on code diversity and time division multiplexing to permit communication between two mobile units I, 2 regardless, within reason, of the proximity of other mobile units sharing the same spectrum. The base unit 1 is usually attached to a vehicle while the remote unit 2 is carried by a user. Both mobile units 1, 2 comprise substantially the same components and monitor the communications environment before and after an RF link 4 has been established. An RF link 4 is established using time slot and SST code assignment performed by consensus between the mobile units 1, 2 on a predetermined "protocol" or ·supervisory" channel. Referring to Figure 2, each mobile unit 1, 2 can be considered to comprise a transmitter 5 and a receiver 6 which both operate under the control of a microprocessor. 8 with input/output control elements. A digitiser 9 and a digital/analogue conversion unit 95 interface the microprocessor 8 with a microphone (audio input) 10 and a loudspeaker (audio output) 11 respectively. Referring to Figures 2 and 3, each unit 1, 2 is operated in transmit or receive mode under the control of a transmitter/receiver (T/R) switch 7 which in turn is controlled by the microprocessor 8 associated with that unit. The switch 7 is shown in SUBSTITUTE SHEET PCf/ AU90/00020 W090/08447 - 9 - further detail in Figure 5, It is a standard component, based on a pair of PIN diodes 20, 21, with a control voltage input 100 from the microprocessor 8 which is high when transmit mode is selected and low when receive mode is selected. Referring again to Figures 2 and 3, the transmitter 5 is provided with a pair of frequency rr.odulated sources (oscillators) 12 operating 1 MHz apart. Each oscillator comprises a known surface acoustic wave (SAW) device designed to oscillate at a frequency of the order of 900 MHz. When the T/R switch 7 puts the relevant mobile unit 1 or 2 into transmit mode, the outputs of the two oscillators 12 are alternately connected to a transmitting antenna IS, via suitable amplifiers 16, 17, according to a predetermined pseudo-random sequence which can be reconstructed by the receiver 6. The selection process effectively impresses a high frequency, frequency modulation {FSK)on the signal FM carrier and spreads the transmitted spectrum in accordance with the speed and characteristics of the chosen pseudo-random sequence. Referring to Figures 7 and 8, audio modulation is applied to each oscillator 12 via the summing input of an operational amplifier 84 in an oscillator arrangement 85 which also maintains the centre frequency of the oscillator. The arrangement provides a voltage controlled oscillator (VeO) and a phase detector which together provide a phase locked loop (PLL). The veo comprises a transistor 71, delay lines 72 and a varacter diode 73. The phase detector comprises a prescaler 74, which operates on the frequency of a crystal oscillator 75 to multiply it " SUBSTITUTE SH£ET PCfI AU90/00020 W090/08447 - 10 - by 256 via an exclusive OR gate 76, and a low pass filter, or op-amp, 77. The phase detector detects the difference in phase between the veo output and the crystal oscillator 75 and a resultant error voltage drives the loop via the low pass filter 77. The low pass filter 77 of the loop is designed to have a cut-off frequency 78 of 100 Hz, whilst the audio modulation has a bandwidth 79 in the range from 5 KHz to 50 KHz. This provides mutually exclusive filtering such that the loop response is not fast enough to affect the audio input, and the audio modulation applied to the sununing input of the operational amplifier 84 does not interfere with the basic loop operation. This allows the centre frequency of ' the oscillatorto be maintained during the application of the modulation. When the relevant mobile unit 1 or 2 is put into receive mode, the ｳ｡ｭｾ＠ pair of oscillators 12 are used as local oscillators for the receiver 6, but offset in frequency by means of a single side band (SSB) up-converter 18 to permit the use of a moderately high first intermediate frequency (IF)a The receiver 6 otherwise comprises the elements of a standard heterodyne receiver, supplemented by components 6A for use in synchronisation, and connections to the microprocessor 8 for use in moni toring the cO!:l.munications environment. Re·ferring to Figure 6, the SSB up-converter 18 comprises a standard component based on a 35 MEz crystal oscillator 22 and configured to eradicate all but a single sideband. Two buffers 23, 24 prevent unwanted reflections of the up-converter output, for instance into the transmitter 5. The crystal oscillator 22 is gated to operate when the unit 1 or r ; SUBSTITUTE SH£ET PCf1AU90/00020 WO 90/08447 - 11 - 2 is in receive mode only, by means of a control input 25 from the microprocessor 8. Referring to Figures 2, 3 and 4, when the mobile unit 1 or 2 is in transmit mode, the digitiser 9, microprocessor and input/output control elements 8 convert a speech signal input to the microphone 10 to the signal FM carrier on which the oscillators 12 impress the SST pseudo-random sequence. The conversion is performed in a series of steps (80 to 83) under the control of the microprocessor 8. These steps comprise: i) digitising the speech signal from the microphone 1.0; ii) formatting and storing data packets from the digitised speech signal, each packet having framing and synchronisation bits added; iii) High speed playback of the stored packets so that each one is time-compressed relative to the directly digitised speech signal; and iv) conversion of the data packets to an 8 bit (256 level) "analogue" form for frequency modulation of the input to the oscillators 12. When the mobile unit 1 or 2 is in receive mode, the same steps are effectively reversed at the audio output 19 of the receiver 6. Overall, the operation of the ｣ｾｵｮｩ｡ｴｯｳ＠ equipment is as follows. When a mobile base unit 1 is operated by a user to establish a communication link 4 with a mobile remote unit 2, it alerts the remote unit 2 by transmitting on a fixed supervisory channel. Both units 1, 2 select by consensus a free channel for voice transmission and subsequent transmission takes ," . SUBSTITUTE SHfET PCfI AU90/00020 W090/08447 - 12 - place via the selected channel. Channels, including the supervisory channel, are distinguished by the SST pseudo-random sequence associated with them. In more detail, during voice transmission from the base unit 1, a speech signal at the microphone 10 is operated on according to steps i) to iv) described above. Thus it is acquired in real time, digitised and stored in a -frame- in a buffer allocated to the transmitter 5, with added ｦｲ｡ｾｩｮｧ＠ and synchronisation bits. When a transmission command is activated, the prepared packet of data is read out of the buffer at approximately 16 times the aquisition rate, converted back to an 8 bit (256 level) -analogue- form and output to frequency modulate the two RF oscillators 12 at rates intbe range of 5 KHz to 50 KHz, with a maximum deviation of approximately 50 KHz. The 256 level -analogue- form used to modulate the oscillator is a known signalling technique in which the signal value is allowed to take one of 256 levels during a sampling interval. The above arrangement permits the ｵｾ･＠ of 8 rather than 16 system time slots since each channel selected must have two time slots assigned to it to achieve two-way communications. Typical packet length may be selected to be 10 m sec, corresponding to 160 m sec of acquired audio, so as to ］｡ｩｮｴｾｲＮ＠ conversation continuity without allowing synchronisation and propagation delay overheads (up to 10 micro sec.) to become significant. The frequency modulated RF output from the oscillators 12 would be capable of being transmitted through a channel 300 KHz wide. However, this spectral occupancy is spread by the imposing of the r SUBSTITUTE SH£ET PCfI AU90/00020 WO 90/08447 - 13 - SST pseudo-random frequency hopping sequence to a channel as wide as relevant authorites may make available. In Australia, this means a channel 13 MHz wide while in the United States, this means a channel 26 MHz wide. The frequency hopping can occur at clocking rates of up to approximately 6 MHz in Australia and 12 MHz in the United States. It has the effect of spreading the transmission spectrum in two ways, firstly because two frequencies are applied but more significantly because the frequency hopping itself generates a series of sidebands representing harmonics. The receiver, on receiving such a signal and being synchronised thereto will then reconstruct the original' audio RF modulation but will further spread any interference effects or noise which is not frequency, hopped according to the selected sequence. There are known code sets for use as pseudo-random sequences in signalling which offer a range of codes sufficiently orthogonal to be clearly distinguished. One such set of codes are known as Gold codes and it is proposed to ｾｳ･＠ Gold code sequences of 127 clock periods in communications equipment according to the present invention. There are 129 such distinguishable Gold code sequences and one of these is reserved for the supervisory channel, leaving 128 channel codes. The code repetition period (127 clock periods at 6 MHz or 12 MHz clocking rate) is thus 21 micro sec. in Australia and 10.56 micro sec. in the United States. The selection of Gold code sequences of 127 clock periods represents a compromise between the number of channels this makes available in addition to the supervisory channel (128 x 8 time slots = 1024 " SUBSTITUTE SH£ET PCfI AU90/00020 W090/08447 - 14 - channels), and the maximum aquisition time necessary for the receiver to establish synchronisation. In order to establish synchronisation from a cold start, the receiver code sequence is time shifted and correlated through 1/2 clock period increments, that is at 2 % 127 = 254 locations in the code sequence. These operations can be performed sequentially by hardware, using a synchronisation detector having a rise time commensurate with the code repetiticn period, and hence total synchronisation time is of the order of 254 x 21 micro sec = 5.3 m sec in Australia and 254 x 10.56 microsec = 2.7 m sec in the United ｓｴ｡･ｳｾ＠ Thus the synchronisation time of the receiver 6 is less than the time taken to transmit a single data packet. The SST coded packet is amplified and applied to the antenna 15 for transmission as an RF signal. Output power is controlled by the microprocessor 8 to provide an adequate signal to noise ratio at the receiver 6, so as to use the minimum power commensurate with an acceptable standard of communication. At the receiver 6 of the remote unit 2, . receiving the above RF signal, the local oscillation is frequency hopped using the same Gold code as that impressed on the RF signal by the base unit 1. The local oscillation is provided by the ｯｳ｣ｩｬ｡ｴｾ＠ 12· of the remote unit transmitter 5, up-converted by 35 MHz to give a first IF of 35 MHz. The RF signal received at the antenna 15 is applied to a preamplifier 30 through the T/R switch 7 and mixed at a DBM 142 ｖ｡ｲｾ＠ L mixer 31 with the frequency hopped local oscillation which is hopped in synchronisation with the oscillators at the base unit 1 which has ; :. SU BSTITUTE SHEET PCfI AU90/00020 W090/08447 - 15 - generated the RF signal. The output of the mixer 31 is thus a despread IF signal at 35 MHz and can be demodulated by a standard IF discriminator 32. The power output of the IF filter/amplifier 33, 34 is indicative of the signal to noise ratio of the incoming RF signal, and of the degree of synchronisation between the two units I, 2, and can therefore be used for diagnostic purposes. Additionally, if the modulating sequence is deliberately dithered in the time domain (shifted repeatedly to and fro in time), synchronisation can be maintained by monitoring the effect of the dither. As mentioned above synchronisation from a cold start is achieved by the known technique of sweeping the receiver code sequence and looking for a match with the code sequence of the RF signal. More specifically, the receiver code sequence is time shifted by 1/2 clock period increments, under the control of the microprocessor 8, and the received power observed. Synchronisation is indicated by maximum power ｾｳ＠ shown by the output of a correlation score registered in the microprocessor in accordance with the received RF signal power. In general, such a process is also known as -aquisition from a cold start-, With regard to ｭ｡ｩｲＮｾｮｧ＠ synchronisation once established, the code sequence applied at either the transmitting unit 1 or the receiving unit 2 is periodically advanced and retarded (dithered). It is. then possible to monitor received power and detect when the two sequences are moving out of synchronisation since when they are synchronised, two power peaks will be observed evenly spaced during ,.• SU BSTITUTE SHiET PCfIAU90/00020 W090/08447 - 16 - each dither period. As synchronisation tegins to slip, the two power peaks will become unevenly spaced until eventually only one power peak is observed. In addition to the above aquisition and synchronisation monitoring facilities, it is of course possible to provide standard error detection and correction procedures, including ｡ｵｴｯｾｩ｣＠ packet retransmission on request, under the ｣ｯｮｴｾｬ＠ of the microprocessor 8 and as extensions of ｴｨｾ＠ described manner of operation. During the establishment, course and termination of a call, the conununications equipment uses the supervisory channel in a series of different ways. This, embodies a controlling protocol for call initiation, duration and termination. The use of the ｳｵｰ･ｲｶｩｯｾｹ＠ channel is as follows. Protocol - (Supervisory) Mode Operation a) Sleep Mode This mode is reserved for the ｰ･ｾｩｯ､＠ when no calls have been or are about to be initia:ed and involves monitoring of the electromagnet:c environment by each receiver, with analysis of traffic and/or interference on each channel. This results in a prioritization of favourable channels in readiness for call initialization. If required, synchronization pulses can be sent and received at periodic intervals on the supervisory channel and status of the link and operational hardware verified in anticipation of call requests. ,i..- b) Initialization Mode ; ｾ＠ . SUBSTITUTE SHEET - :------------------.-- PCf/ AU90/00020 W090/08447 - 17 - This mode is used to establish call initiation by use of the supervisory channel. The first objective is to prepare both units 1, 2 for an orderly data transfer. This includes the decision on a mutually agreeable code, verification of hardware operation and synchronization, advance information regarding imminent data transfer and the decision as to which unit 1, 2 will go first into transmit mode. Diagnostics relating to the quality of the link can be gathered e.g. fades and multipath and corrective action taken as required. c) Data Transfer Mode Although the major task being performed in this mode is associated with the act of communication, there are certain supervisory activities which also have to be sustained. In particular, the system must maintain vigilance in order to prevent contention problems from arising (it being possible for units to establish contact under benign conditions and then to drift into each other's zones as a result of user motion). Contingency measures such as back-off and reassignment have to be implemented and coordinated in order to avoid cross talk. Automatic retransmission on request can be employed to retransmit corrupted data if appropriate. On call termination, the supervisory operations return to sleep mode. Overall however, in data transfer mode the supervisory channel is left substantially free for use by other, independent users. Referring to Figures 2, land 8, as described above, the operation of the communications r, SUBSTITUTE SH£ET PCfI AU90/Q0020 W090/08447 - 18 - of the equipment is under the overall ｣ｯｮｴｲｾ＠ microprocessor 8. This control is ｩｭｾｬ･ｮｴ､＠ as follows. Signals to be output from the transmitter 5 require application of a code sequence whether relevant to a supervisory channel or ｾ＠ a data transfer channel. The microprocessor 8 determines the code sequence to be applied and ｣ｯｾｴｲｬｳ＠ an electrically programmable logic device (E?LD) 41 to supply the selected code sequence to ｴｾ･＠ oscillator pair 12. The c?'igi tised signal is formctted and s.tored in a transmitter (TX) buffer 42. from which it is read out at 16 times the aquisition rate under a clock control input 43 from the ｭｩ｣ｲｯｰｾｳ＠ 8. The 8 bit (256 level) "analogue" conversion is then performed on the high speed read out froca the buffer 42 and the signal is supplied to the ·Audio Modulation Data In· terminal 44 of the transmitter 5. The microprocessor 8 also controls the output power of the transmitter 5, via ｾ･＠ power amplifier 17 between the transmitter 5 ｾｮ､＠ the T/R switch 7. It does so by means of a cha=;e pump 90, that is, a gated integrator, as known f:r instance for use in remote control of television loudness or brightness. In the receive mode, the microprocessor 8 receives the output of the IF ､ｩｳ｣ｲｭｮＺｾ］＠ 32, again via a digitiser 46. It also receives po-er information from the RF signal at correlation and dither inputs 47, 48 for use in establis:ing and monitoring synchronisation. The code sequence to be applied for despreading the signal is again determined by the microprocessor 8 and applied to the oscillator pair r l SUBSTITUTE SH£ET PCf/ AU90/00020 W090/08447 - 19 - 12, and thus to the local oscillation for the receiver 6, by means of the EPLD 41. The received signal packets are then transferred to a receiver (RX) buffer 49 and read out at low speed (divided by 16) to provide are-expanded output signal for analogue conversion, filtering, and playback at the audio output 11. The microprocessor 8 controls tte receiver gain at the IF amplifier 34, again by use of a charge pump 91, and determines whether the associated unit I, 2 is in transmit or receive mode by two further dedicated control outputs 92, 93 . . Overall, embodiments of the present invention provide a secure, adaptive form of communication which can be used in a wide range of environments. A range between mobile units 1, 2 of from 2.5 ｾ＠ to 10 km in free space can be achieved, with the ability to o£fer more than 1000 independent channels. The mutually orthogonal Gold codes selected iend themselves to unscannab1e communication far superior for security purposes to narrow frequency band communication. Many modifications will be apparent to those skilled in the art ,without departing froe the scope of the present invention as hereinbefore described with reference to the accompanying drawings. Standard techniques such as dia:ling processes, and details of actual signal ｾｲｯ｣･ｳｩｮｧ＠ steps such as digitising, delta modulation, data compression and silence detection, are not described since these are all known techniques and steps. Further, it will be clear that specific part numbers or values indicated on the drawings should not be treated as essential features of the invention. " SUBSTITUTE SHl!ET PCfI AU90/00020 W090/08447 - 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Mobile units 20 - 1, 2 for use in equipment according to embodiments of the invention can be designed to fit the stringent requirements of size, weight, power consumption and cost constraints that may be applied to a portable, time hand-held communications unit while at the same offering good quality, secure communication in a wide range of environments. The adaptive power and gain control minimises the overall electromagnetic disturbance created by the units while the signalling regime described provides enhanced resistance to fading and interference and multipath rejection. By implementing short duty cycles, it is conserve ｢｡ｴｾｲｹ＠ life. possible to r9 Figures 10, 11 and 12 illustrate an alternative embodiment of the invention. The same reference numerals have been used to denote parts which correspond to those of the previous embodiments. 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Figure 10 generally corresponds to the system illustrated in Figure 3. The principal difference however is that the pair of frequency modulated sources 12 of Figure 3 is replaced by a carrier oscillator 200 which has a frequency of 921.5 MHz the output of which is coupled to an FM modulator 202. The modulator 202 receives input from the digital to analog converter 45 which corresponds to the same element in Figure 8. Output from the modulator 202 passes to a bi-phase modulator 204 which also receives input from a pseudo-random noise code generator 206 which in turn receives input from an oscillator 208 which has a frequency of 26 MHz. The bi-phase modulator 204 corresponds generally to the switch 13 of Figure 3 except that instead of switching between the frequencies of the oscillators 12, the modulator 204 reverses the phase of the signal from the FM 36 modulator 202. The resultant signal passes 37 38 SUBSTITUTE SHEET through the PCfI AU90/00020 W090/08447 - 21 1 2 amplifier 17 and switch 7 to the antenna 15. The signal analogous to a DSB suppressed carrier signal. is 3 4 5 6 The receiver 6 is again similar to the receiver arrangement illustrated in Figure 3 except that the receiver has its own oscillator 210 having a frequency equal to the 7 8 sum of the carrier and intermediate frequencies i.e. 956.5 MHz. Its output is coupled to a bi-phase modulator 212 9 10 11 12 13 connected to the despreading mixer 31. The modulator 212 and intermediate frequency amplifier 34 are controlled by a code tracking loop 214 which is functionally equivalent to the up-converter 18 of Figure 3. The code tracking loop 214 includes a clock generation and control circuit 216 the 14 15 output of which is coupled to a PN code generator 218 the output of which is, in turn, connected to a dither generator 16 17 18 19 20 21 22 23 24 220. The circuit 216 includes a dither clock output 219 which is also connected to the generator 220. Output from the generator 220 is inputted to the bi-phase modulator 212 as shown in Figure 10. The loop 214 also includes a carrier detection and AGe circuit 224 which corresponds generally to the component 6A of Figure 3. 25 ways and the circuit illustrated is by way of example only. 26 27 28 29 Figure 11 illustrates in more detail the code tracking loop 214. This circuit could be implemented in a variety of Figure 12 shows one cirQuit realisation for the circuit 224. The circuit includes an integration control logic circuit 230 the truth table of which is set out below. 30 31 32 33 34 35 36 37 38 SUBSTITUTE SHfET PCfI AU90/00020 W090/08447 - 22 1 2 TRUTH TABLE FOR INTEGRATE CONTROL LOGIC 230 3 4 5 Detector Enable Dither Clock Invert Non-Invert Mode 6 7 8 9 o o o 1 Integrate 1 1 o o 10 11 12 ·1 o o 1 13 Dump 14 o o 1 15 16 17 18 The operation of the arrangement of Figure 10 is 19 similar to that of Figure 3 and therefore need not be 20 described in detail. Briefly its operation is as follows. 21 22 During transmission, the information signal (voice or 23 data) from D/A converter 45 frequency modulates a carrier at 24 921.5 MHz from oscillator 200. The resulting signal is bi25 phase modulated in, modulator 204 by a PN code sequence 26 generated by the PN code generator 206 at a rate of 6.5 MHz. 27 The resulting spread spectrum signal is amplified by 28 amplifier 17 and transmitted via the antenna 15 to the 29 receiving unit. Transmission power is controlled by means 30 of manual adjustment of the transmitter power amplifier 31 gain. 32 33 At the receiver, the received spread spectrum signal 34 received by the antenna 15 is filtered and amplified before 35 being despread by the receiver's "local reference code 36 sequence in mixer 31, which is synchronized to the 37 transmitted modulating code. The resulting despread signal 38 SUBSTITUTE SH£ET PCf1AU90/00020 WO 90/08447 - 23 1 is FM demodulated by discriminator 32 2 original information signal at output 19. to recover the 3 4 During signal reception, carrier 5 provides 6 7 uses the information to take adaptive maintaining overall system performance. detection circuitry signal diagnostics to the microprocessor 8, measures, which thereby 8 9 10 11 12 The microprocessor 8 issues control signals to clock generation and control circuitry 216, to control phase and frequency of the receiver's code generator code synchronization. 13 14 15 16 17 18 the the for The code tracking loop 214 performs three basic functions: 1. Initial Synchronization Tracking 2. Automatic Gain Control 3. 19 20 21 22 23 24 During initial synchronization, the receiver· 6 is receiving a maximal length code modulated carrier, sent by the transmitter. To acquire synchronisation, the receiver performs a phase search of its local reference code sequence until the point of maximum correlation is found. The phase 25 26 searching process is controlled by the microprocessor 8, with code phase shifts initiated by means of "retard" and 27 "advance" control signals. 28 29 The phase search process consists of acquiring the 30 31 32 level of correlation for each 0.5 bit phase shift of the local reference code sequence' over the entire length of the code sequence. The carrier level provides an indication of 33 34 the level of microprocessor 35 36 and and correlation and is made available to 8, using a square law detection circuit the 232 low pass filter 234, as ·an analog signal to be sampled digitized. The carrier detection circuity aa-prising 37 38 SUBSTITUTE SHEET PCfI AU90/00020 W090/08447 - 24 1 the square law detector circuit 232 and low pass filter 2 is also shown in circuit realisation of Figure 12. 234 3 4 For a cordless telephone extension the remote unit is 5 generally the same as that described previously and the base 6 unit 7 switched telephone network. 1 would be adapted to directly connect to the public 8 Although 9 10 11 12 relation could the embodiment described above to audio signals, any relatively slow be transmitted on an RF link according to arrangement. 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 ; ;":- SUBSTITUTE SH£ET operates in data input the above PCf/ AU90/00020 W090/08447 - 25 1 CLAIMS 2 3 1. 4 mobile unit (2) incorporating transceiving means (5,6), 5 6 a second unit (1) incorporating transceiving means (5,6) and coupling means (3) for connecting the second unit (1) to a 7 8 9 10 telephone switching system or network, the transceiving means of the first and second units being adapted for establishing a communication link (4) between them, wherein either the first, mobile unit or the second unit further 11 12 incorporates a sensing means (6,8), characteristics of the communication link 13 equipment further comprises feedback and control means (5,8) 14 15 16 for controlling aspects of said link (4) in response to the sensed ｣ｨ｡ｲｴｾｩｳＬ＠ such that the link is adaptive in accordance with its communications environment. 17 18 19 20 21 22 23 24 25 26 Mobile communications equipment comprising for (4), a first, and sensing and the "' Mobile ' communications equipment according to claim 1 2. wherein said sensing means senses characteristics of the link after the link has been established, such that the link is dynamically adaptive in accordance with its communications environment. Mobile communications equipment according to either 3. preceding claim wherein said characteristics comprise a level of interference or noise associated with the link. 27 29 communications equipment according to Mobile any preceding claim wherein said characteristics comprise signal 30 power being received over the link. 28 4. 31 32 33 34 35 5. communications equipment according to Mobile any preceding claim wherein said coupling means comprises means for connecting the second unit to a low data rate port of a telecommunications network. 36 37 6. Mobile communications equipment according to 38 r SUBSTITUTE SHfET claim 5 PeTl AU90/00020 W090/08447 , - 26 1 wherein said port comprises an audio input/output port. 2 3 4 5 6 communications equipment according to any Mobile 7. preceding claim wherein said coupling means comprises means for connecting the second unit to a public switched telephone network. 7 8 9 10 11 8. Mobile communications equipment according to any preceding claim wherein said coupling means comprises means for connecting the second unit to an audio input/output port of a cellular telephone system. 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 communications equipment according to Mobile 9. preceding claim wherein said second unit is mobile. any communications equipment according to any 10. Mobile preceding claim wherein said first unit is a portable, handheld unit. 11. Mobile communications equipment according to claim wherein said first unit incorporates said sensing means. 10 12. Mobile communications equipment according to any preceding claim wherein either the first unit or the second unit comprises said feedback and control means. 13. Mobile communications equipment according to anyone of claims 1 to 11 wherein said first unit and said second unit together comprises said feedback and control means. 30 31 14. 32 preceding claim wherein said first unit and said second unit 33 34 each incorporate a sensor for sensing characteristics of the radio communication link once established, and said feedback Mobile communications equipment according 35 -and control means controls aspects of said link in 36 to the output of both sensors. 37' 38 r SUBSTITUTE SH£ET to any response PCfI AU90/00020 W090/08447 - 27 - 1 2 15. Mobile communications equipment according to claim wherein said feedback and control means comprises 14 a 3 4 microprocessor which receives and analyses the output of the sensors. 5 6 16. Mobile communications equipment according 7 8 preceding claim wherein said aspects of the link comprise power and gain levels of the respective transceiving means 9 of the first and second units. to any 10 11 17. 12 13 14 preceding claim wherein said first and second units comprise means for selecting a communication channel on which a radio communication link is to be established and said feedback 15 16 and control means comprise means for changing the selected communication channel on which a link has been established. Mobile communications equipment according 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 SUBSTITUTE SHEET to any PCfI AU90/00020 W090/08447 - 28 - lB. Mobile communications equipment according to any preceding claim wherein said link is established . by means of a spread spectrum signalling technique. 19. Mobile communications equipment according to claim 18 wherein the transceiving means of each unit comprises a plurality of oscillators having different output frequencies and spreaj spectrum signal transmission is achieved by switching sequentially between the outputs of the oscillators according to a preselected pseudo random code. 20. oMobile communications equipment according to claim 18 wherein the transceiving means of each unit can act either in transmit mode or in receive mode, and comprises a plurality of oscillators whose output is controlled to provide the spread spectrum signalling in transmit mode, the transceiving means operating as a heterodyne receiver when in receive mode, the output of the plurality of oscillators then being applied to the transceiving means via a frequency conversion device se .as to provide local oscillation and an ｩｮｴ･ｲｭ､｡ｾ＠ frequency for the heterodyne receiver. ｾＮＭ 21. A mobile unit for use in mobile com.rnunications equipment comprising transceiving means for establishing a comcunication link with another such unit, wherein the mobile unit incorporates a sensor for sensing characteristics of the link, and feedback and control means for controlling aspects of said link in response to the sensed characteristics, such that the link is adaptive in accordance with its communications I SUBSTITUTE SHEET PCfI A1190/00020 WO 90/08447 - 29 - environment. 22. A mobile unit according to claim 21 wherein said sensor senses characteristics of the link after it has been established, such that the link is dynamically adaptive in accordance with its communications environment. 23. A ｾｯ｢ｩｬ･＠ unit according to either of claims 21 or 22 wherein said link is established by means of a spread spectrum signalling technique. 24. A mobile unit according to any of claims 21, 22 or 23 further comprising a switch, the transceivinq means operating in transmit mode or in receive mode under the control of said switch the transceivinq means operating as a heterodyne receiver when in receive mode, the unit also comprising oscillation means whose frequency output is used directly when the transceiving means operates in transmit mode and is used via a frequency up-converter when the transceiving ｾ･｡ｮｳ＠ operates in receive mode, the frequency up-converter providing a fixed increase in said frequency output which can be used as an intermediate frequency for said heterodyne receiver. l ! SUBSTITUTE SH£ET PCf1AU90/00020 WO 90/08447 1/11 15 15 1 2 3 FIGURE 1 SUBSTITUTE SHlET W090/08447 PCfI AU90/00020 2/11 7 _----l T/R SWITCH 6 5 TRANSMITTER RECEIVER MICROPROCESSOR AND INPUT I OUTPUT CONTROL ELEMENTS ""':>----1 10 01 GIT 1SER J...--1 8 AUDIO OUT O/A CONVERTER 9 94 FIGURE 2 SUBSTITUTE SHEET 11 12 ＱｾＮＺＭ｟＠ Ｎ｟ｬｾｲ［＠ I ｾｦＧＭ＼ｉ＠ 5 A' . I ...---. I, __. I Ｍｾ＠ -=..' ::.' i 1 ｾＭＬ＠ ...... 31 -= ::...:.._.. :. -=..' ｾ＠ ! t -.) I i i '> I = = \C I .... ｾ＠ GAIN (ONTROL i I I FIGURE 3 1 I I YR II I I I I I __ . .:. _-' I , 1 Cf I I'; t ｾｴ＠ 1 I 33 34 -I) U) =ii c! -It ......... rni I IN Vtt Fe :I:i J)l{ 1'1·3 .. ·,,1 I I Dithered L----------------4, '-'T'-'-'-'-'-' -.-.-..: I l._._. _.-.; I . , I I I , _------L---(_______ I I ｾ＠ I I : : I L- - - - - - ｾＸ＠ I --L 6A\ SEQUENCE To Dither Processor --L lOW PASS ｾ-＠ , . - IFILTER IIF 0 DISCRIMINATOR ...-,c." ｾ＠ r'JIJ I Dither (2nd Hannonic) AUDIO OUT ....___ I . Correlation Score ＠ｾ _ _ _ _ ＮＡｯｾ＠ ａｃｑｵｩｳｴｾｮ＠ ____________ -\ ______ J ,.... - - - - - - -1 Ｖｾ＠ -J - J 32 19 "'t:l 8>c:! \C = ..... = = = N o PCf/ AU90/00020 W090/08447 4/11 DIGITISING 81 82 83 PACKET FORMATTING STORAGE AND ENCODING MICROPROCESSOr< Af'lJ INPU T/OUTPUT CONmOL ElB-1ENTS PLAY BACK {HIGH SPEED } 8 ANALOGUE CONVEnSION TO OSCIUATORS 12 FICiJRE SU BSTITUTE SHlET - -_ _ _ _ _ _ _ _ _ _ _ _ ｾｲＮ＠ 4 W090/08447 PCf/AU90/00020 5/11 FIGURE 5 15 TO RECEIVER >-----11-----1------.1 FROM TRANSMITTER 20 ｾＭＴ＠ 21 COMBINER PS 2- 2000F ANAREN 10330- 3 H 90° Y B R I D CO 24 0° 90° HYBRID ANAREN '--_-......110230-2 FIGURE 6 SUBSTITUTE SHEET PCfI AU90/00020 W090/08447 6/11 I 11 ( 85 RF OUT 14 256 h. -L I FIGURE 7, SUBSTITUTE SH£ET R ｾ＠ ｾＱＵ＠ t-<AUDIO IN 3·59MHz W090/08447 perl AU90/00020 7/11 10 FIGURE 8 ＾Ｍｾｆｉｌｔｅｒ＠ ｾ＠ 46 47 90 .,. POWER AID MICROPROCESSOR 4S AID GAIN 41 CODE SELECT TX -' 91 CLOCK 93 43 CLOCK TX BUFFER 43 49 RX BUFFER CLOCK LOW PASS FILTER LOW PASS FILTER "" "" 45 AUDIO OUT TRANSMITTER SUBSTITUTE SH£ET 11 --- W090/08447 PCfI AU90/00020 8/11 G z w a w tt: -0\ ::r: 8 ｾ＠ UJ V) Z ＠ｾ UJ c::. V) SUBSTITUTE SHiET .. " ,..---------- - - - - -- -- 202 , I '-- - -I -I C -I ｲＭｾ＠ CIt I i 1ft 8 I 206 MICROCONTROLLER CLOCK GE;NERATOR -L - - - - - PM CODE GENERATOR 219 224 r-- IF GAIN I I I & AGC _ J 33 FIGURE 10 T/ " 220 CO ......... -J. R -J. 7 : I ____ J 212 I IF BI-PHASE .....1 - - - - - 0 ( MODULATOR 210 30 34 IF AMP 15 -2;S-1 - DITHER GENERATOR CA.RRIER DETECTION INFORMATION OUT • ｾ＠ CODE CLOCK ｃｏｎｾｒｌ＠ ｾ＠ ...... _-.J ｾＱＴ＠ -216-- 8 I I -------------- III -I PN CODE GENERATOR ｾ＠ I I I I r'S POWER AMP- XTAL OSC I III ｾ＠ CARRIER 208 I I BI-PHASE MODULATOR' 200 I Ｎｾ＠ I I 17 AMP I I I - -- -- -- -- -- -- --, ｾＴ＠ FM MODULATOR AUDIO • 45 I - "t1 8> c::: \Q = ....... DESPREADING MIXER BF PREAMP = = N = = .' . 8 t- , RESET ｾ＠ MICRO- '"ｾ＠ CONTROLLER I CLOCK I '.J L =i CODE CLOCK OCK DITHER CL • .: .: _____ _ A/O AID n L1 : I -PHASE MODU LATOR J I-' o "I-' ｾｇ＠ _ V I-' L _ _ __ _ I I ｾ＠ SYNCHRONOUS DETECTOR lot- 2}4 1LPF ｾ＠ 2}2 : d SQUARE LAW ..1----DETECTOR II -.J FROM IF STAGE Io'!::I ..... TO IF AMP I I I .I I FIGURE11 I ｾ＠ ..... ｾ＠ I · DLA CONTROL TO E : 1 D/A I _ I 230 INTEGRATION ｾ＠ . CONTROL ; LOGIC DITHER ERROR I INTEGRATE I aDUMP CARRIER LEVEL IF GAIN V 224 I INTEGRATION CONTROk DITHER GENERATOR ｾＭ CARRIER DETECTOR ｾ＠ -I -.I I -------------- In t 220 II --' L I '" = I D/A - en GENERATOR ｾＲＱＸ＠ 1 I i I -I PN CODE ｾ＠ II I I'll iE ｾ＠ I 1 I VCO D/A CONTROL . : I VCO FREQUENCY c:: I LOGIC J.:. 4 ｾ＠ 214 L DITHER ENABLE ｾｃ＠ c:: 1 , ｃｏｎｔｒｾＲＱＶ＠ I SEQUENCE END DETECTION I CLOCK ｾＭｉＧｃｏｎｔｒｌ＠ & I RETARD ENABLE ADVANCE ENABLE en =--NERATION .=-.=. Ｍｾ＠ ｾ＠ = '" = N = = = '" . ｾ＠ ! <= '" ; I 224 31.6KHz DITHER CLOCK 230 INTEGRATION CONTROL ｌｏｇｉｃｾ＠ 1---------------- , I , I : DITHER CLOCK DETECT. It mi , v DETECTOR ENABLE I LJ L ____________ _ I-' I-' CIt, " SQUARE LAW DETECTOR %1 ,,"7 FROM IF STAGE RECTIFTF.R ｾ＠ -)--1-- r ....... 234 232 I ｲｴＭｾ＠ DETECTOR CLOCK CONTROL I L.I> I Ｚ＠ｾ =if '" . -I' I - INTEGRATE/DUMP -,'C:: = ｾｬ＠ t INTEGRATE CONTROL ｾ＠ ..... ..... r--If---,/ I ｃａｾ［ｲｏｒ＠ COUPLING LOW PASS FILTER INVERT INTEGRATOR SYNCHRONOUS DETECTOR CARRIER J.EVEL FIGURE 12 "tI DITHER CODE 8>c:: \0 C C '" :> c N C SEARCH ｉｎｾｅｒａｔｏｌ＠ ｒｅｐｏｾｔ＠ International Application No. I. CLASSIFICATION OF SUBJECT MATTER PCT/AU 90/00020 I (if severaL cLassification symboLs appLy, indicate aLL) 6 I According to International Patent Classification (IPC) or to both National Classification and IPC Int. C1. w n. 5 H04Q 7/04, H04M 1/72, H04B 7/26 FIELDS SEARCHED Minimum Documentation Searched 7 Classification System Classification SymboLs H04B 7/00, 7/005, 7/26; H04M 1/72; H04Q 1/32, 1/39, 7/04 379/60,61,63,58,59 IPC US Cl. Documentation Searched other than Minimum Documentation to the Extent that such Documents are Included in the FieLds Searched 8 AU IPC as above TIl. 1XlCUMENI'S CONSIDERED TO BE RELE.VANT 9 tt X,Y X,Y X,Y X,Y X,Y· Y Y * I I I I I I I I "A" "E" "L" \ \ I "0" -\ I I I I "P" ----- with indication, where appropriate, Citation of Document, of the relevant passages 12 Category* I I I I I I I I I I I I I I I Relevant to CLaim No 13 EP,A, 244872 (NEC CX>RPORATION) 11 Novanber 1987 (11.11.87) (1-24) Patents Abstracts of Japan, E-392, page 18, JP,A, 60-226232 (NIPPON DENIa. K.K.) 11 Novanber 1985 (11.11.85) (1-24) US,A, 4613990 (HALPERN) 23 September 1986 (23.09.86) (1-24) US,A, 4639914 (WINTERS) 27 January 1987 (27.01.87) (1-24) US,A, 4751725 (BONTA et al) 14 June 1988 (14.06.88) (1-24) EP,A, 112108 (RACAL-SES LIMITED) 27 June 1984 (27.06.84) (18-20,23) EP ,A, 219085 (AMERICAN TELEPHONE AND TELEGRAPH Ga1PANY) 22 April 1984 (22.04.84) (18-20,23) SpeciaL categories of cited documents: 10 IIT" document defining the generaL state of the art which is not considered to be of particular relevance earlier document but published on or ·X" after the international fiLing date document which may throw doubts on priority claim(s) or which is cited to establish the publication date of another citation or "Y" other special reason (as specified) document referring to an oral disclosure, use, exhibition or other means document published prior to the international filing date but later than the priority date claimed - "&" Later document pubLished after the internationaL filing date or priority date and not in conflict with the appLication but cited to understand the principle or theory underLying the invention document of particular reLevance; the cLaimed invention cannot be considered noveL or cannot be considered to involve an inventive step document of particular relevance; the claimed invention cannot be considered to involve an inventive step when the document is combined with one or more other such documents, such combination being obvious to a person skilled in the art. document member of the same patent family I I I I I I I I I I I I I I I I \ ｬ -------------------------------------------------------------------1 Date of the ActuaL CompLetion of the Date of Mailing of this International ＭｎＮｾｔｬｩｮｏﾷ International Search Search Report ＱｾＹＰ＠ 1 May 1990 (01.05.90) Authorized Officer International Searching Authority Austed ian Patent Office Form PCT/ISA/210 (second sheet) (January 1985) R. CHIA . . ./?"z::. 'c:- .. ANNEX '10 '!HE INrERNATICNAL SEARCH REPCRI' INrERNATIOOL APPLICATIOO roo rn PCI'/lill 90/00020 '!his Annex lists the knc7.m "A" publication level patent family nanbers :relating to the patent doc:unents cited in the al:xJve-nentioned intemational search report. '!he Australian Patent Office is in no way liable for these particulars which am nm:ely given for the purpose of infonnation. Patent D:x::l.ment Cited in Search Report Patent Family Manbers EP 244872 AU 72695/87 US 4837801 us 4613990 CA 1235188 JP 61502576 CA 1267737 JP 62262528 EP 186684 8600486 HK 48/90 l\O us 4639914 AU 50790/85 JP 61139135 CA 1257416 EP 184383 us 4751725 EP_ 299040 JP 1502071 VI) 8805987 EP 112108 lill 22223/83 GB 2132452 R) 834506 CA 1252822 JP 62099000 US 4580262 EP 219085 us 4672658 END OF ANNEX