GB2270817A - Communication system - Google Patents

Abstract

A communication system includes a portable unit with which a transceiving device is associated for sending digital information via a first signal. A communication controller receives the first signal, and transmits a second signal which utilises a cellular telephone link, the second signal being based upon the first signal. A host computer receives the second signal. A third signal is transmitted from the monitor to the communication controller utilising the cellular telephone link. A fourth signal, which corresponds to the third signal, is transmitted from the communication controller to the transceiving device. Each transceiving device has the capability of sending and receiving data information and monitors and/or controls the operation of distinct portable units such as compressors. The necessity for land lines between the communication controller and the portable units is avoided. <IMAGE>

Description

2270817 COMMUNICATIONS SYSTEM This invention relates generally to

communication systems including cellular telephone linkages, and more particularly to data transmission utilising a cellular telephone linked to a communication controller located at a remote location, the communication controller being in communication with a transducer portion utilising radio communications.

Present cellular telephone systems permit communication between multiple transceiver units. A single cellular telephone is necessary for each transceiver unit.

Therefore, it would be preferable for more than one transceiver unit to be able to share the cellular linkage so that more than one of several portable producing units (for example portable compressors or portable drill rigs) could use the same cellular telephone communication links for transceiving data.

Present cellular data transmitting systems which transmit to multiple portable units use a plurality of land line linkages between the communication controller and each portable unit.

This situation arises where more than one portable unit will be concentrated about a specific location or work site. It is often desired to relocate each portable unit about the work site as the work progresses or changes without having to worry about the land lines. It is also essential to ensure that each portable unit is operating suitably, and to be able to provide commands to effect the operation of each of the portable units individually from a remote location.

2 Presently known systems are not capable of this type of monitoring or control of large groups of remote portable units utilising a few cellular telephone linkages while permitting mobility of the portable units about the work site without including attached land lines.

According to one aspect of the present invention, there is provided a communication system comprising:

a portable unit; transceiving means, associated with the portable unit, for sending digital information via a first signal, the first signal being transmitted through free space; communication controller means for receiving the first signal, and transmitting a second signal which utilises a cellular telephone link, the second signal being based upon said first signal; and host means for receiving said second signal.

According to a second aspect of the present invention, there is provided a communication system comprising:

a portable unit; transceiving means, associated with the portable unit, for sending digital information via a first signal; communication controller means for receiving the first signal, and transmitting a second signal which utilises a cellular telephone link, the second signal being based upon said first signal, the first and the second signal capable of being transmitted at different transmission rates; and host means for receiving said second signal.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 is a schematic view illustrating an embodiment of digital communication system including a cellular telephone linkage; Figure 2 is a flow chart illustrating one embodiment of logic utilised by a communication controller where third and fourth signals are interrogation signals; Figure 3 is a flow chart illustrating an alternative embodiment of logic utilised by the communication controller where the third and the fourth signals are reactive signals; Figure 4 is an embodiment of operation protocol utilised by the communication controller in transmitting data; and Figure 5 illustrates an embodiment of the memory utilised in the control units 20 and 34 of the Figure 1 embodiment; and Figure 6 illustrates an embodiment of logic flow chart for auto retrain.

A digital communication system is illustrated generally at 10. Included in the digital communication system is a host portion 11 (which has the capability of sending and recovering digital data information), one or more communication controller portions 12. one or more transceiving portions 14 (which typically has the capability of sending and receiving data information) and one or more portable units 16 which each transceiving portion 14 is associated with and connected to. Each transceiving portion 14 preferably monitors and/or controls the operation of a distinct portable unit 16.

The portable unit 16 is typically a portable compressor, drilling equipment, abrasive blasting equipment, or other similar device from which it is desired to transmit data information relating to operating parameters to some remotely located host portion 11 or communications controller 12, and also control the operation from the host portion 11 or communications controller located at some remote location. Often there are a plurality of portable units associated with a specific work site or factory which are located within a close proximity to each other. Due to changing work conditions or functions, it is often desirable to reposition the portable units to different locations within the same work site. It is highly desirable to ensure the ease of portability, while maintaining the capability to continually monitor and/or control the operation of the portable units 16. The present invention permits a plurality of portable units 16 to send data information to (or receive data information from) the host portion 12 utilizing the same communications controller 12 at approximately the same time. If an eight bit ASCII code address is utilized, it is possible that 256 distinct portable units may be controlled by a single communications controller at a single work site.

It is rare, however, that more than ten portable units will be located at the same work site.

It is envisioned that the portable units 16 which may be controlled by a single communications controller 12 may be either distinct from each other, or associated with each other. For example, more than one portable units may be related to the same process wherein alteration of the operation of one of the portable units will effect the desired operation of another of the portable units (as may occur where multiple portable compressors are being successively used in different steps of the same chemical process). Under certain circumstances, there may be two portable units which are operationally directly connected to each other (for example a piece of drilling equipment and a compressor which applies compressed air to the drilling equipment). Under these circumstances, the communications controller would have to be programmed to deal with these associations between the portable units. It is possible that these two interrelated portable units 16 may be directly controlled by a single transceiver portion 14.

Typically, the communication controller portion 12 is located in relatively close proximity (within half a kilometer) of all of the portable units 16 which carry transceivers associated with the same communication controller portion 12. All of the communication controller portions 12 may be separated from the host portion 11 a great distance (several thousand kilometers or more). It is envisioned that one host portion may be able to regulate and/or monitor the operation of several thousand portable units 16.

Each portable unit is associated with a transceiver portion 14 which incorporates the control unit 20, each control unit is capable of controlling the operation of, and monitoring, the output from the portable unit 16. The control unit 20 is typically a microprocessor or microcomputer, with a suitable chip being the Intel SOC196 (Intel is a trademark of the Intel Corp.).

An A/D converter 19a is necessary to translates the analog signals produced by sensors (not illustrated) associated with the portable unit 16 into digital signals of a format which may be utilized by the control unit 20. similarly, a D/A converter 19b translates the digital signals from the control unit 34 to analog signals which may be utilized by devices (not shown) associated with the portable unit 16. Typically, a sensor (not shown) is associated with the portable unit to provide a signal which may be translated by the A/D converter 19a. Even though the control unit 20 is capable of operating the portable unit independently (as is highly desirable when the portable unit 16 is not being operated independently of the host portion 11 and/or the communications controller), it is also highly desirable to be able to control and monitor the portable unit 16 from a remote location, at the host portion 11. Whichever operating parameters are desired to be transmitted may be transmitted to the host portion 11 via the communication controller portion 12 in a manner which will become evident by the remainder of this specification.

The transceiving portion 14 includes the A/D converter 19a, the D/A converter 19b, the control unit 20 which is typically microprocessor based (associated with a volatile memory unit 25a, a non- volatile memory unit 25b, and a program memory unit 25c, all of which will be described below), a modem 21, and a first radio portion 30. The first radio portion 30 is capable of transmitting data information to and receiving data information from the host portion 11 via the communication controller portion 12. While the first radio portion 30 and a second radio portion 32 (incorporated in the communication controller portion 12) is preferably designed to operate on the UHF radio band, the present system may function utilizing other radio frequency bands.

The communication controller portion 12 includes the second radio portion 32, which receives from and may transmit to the first radio portion 30; a modem 33; a control unit 34; a modem 35; a first cellular telephone unit 40 and possibly portions of a land line bypass device 80 described below. The control unit 34 is a microprocessor or microcomputer, with the Intel 80C196 being a suitable chip. The control unit is associated with three memor y portions (a volatile memory unit 35a, a non-volatile memory unit 35b, and a program memory unit 35c, the function and structure of all of which will be described below). The first cellular telephone unit 40 is capable of transmitting data signals to and receiving data signals from a second cellular telephone unit 44 directly, the second cellular telephone unit 44 being located in the host portion 11. Alternately, a public switched telephone network system, of a type similar to that illustrated in U.s. Patent No. 4,965,821 issued to Bishop et al. on October 23, 1990 (incorporated herein by reference) may be used by the host portion 11 to access the first cellular telephone unit 40 of the communication controller portion 12. The first cellular telephone unit 40 and the second cellular telephone unit 44 are configured to transmit radio signals utilizing a network of cell patterns, which 10- permits signals to be transmitted over a wide area, as is well known in the cellular telephone art. often the first cellular telephone unit 40 is a roamer unit while the second cellular telephone unit 44 is a home unit, using known nomenclature. The frequencies, applications and utilizations of cellular telephones are well known and will not be further detailed here.

The first radio portion 30 and the second radio portion 32 are identical units. Both of these units 30, 32 typically consist of UHF radio transceivers coupled to modems 21, 33 respectively as are known in the art. The modems 21, 33 permit data information interface between the radio portions 30, 32 and their respective control units 20, 34.

The host portion 11 includes the second cellular telephone unit 44, a modem 60, and a personal computer 64. The personal computer in this disclosure is intended to cover both personal computers of a type well known in the art, as well as more complex computers which are used for this purpose. The modem 60 permits modulation of data signals originating from the personal computer 64 to be transmitted by the second cellular telephone unit 44, and demodulation of a radio frequency signal received from the telephone into a digital signal into a form which may be utilized by the personal computer 64.

The selection of modems for the present application is critical. Modems 60 and 35, which transmit a considerable amount of data, are exposed to widely varying signal qualities and are required to perform under high reliability and at high speeds. Modems 60 and 35 are configured with CCITT (International Telegraph and Telephone Consultive Committee) standards V.42 and MNP (Microcom Networking Protocol) 1 through 4 and 10, as iswell known in the modem art. These protocols perform message integrity checking, verification and/or automatic retransmission. considering that data transmission signal quality from the transceiver portions 14 associated with portable units 16 are highly variable, it is essential that the signals undergo the integrity checking, verification and/or automatic retransmission associated with these protocals.

Modems 60 and 35 are also configured to disable the MNP5 and CCITT V.45bis compressional protocols (or other compressional protocols). Since each data signal transmission related to portable unit 16 signal transmission has a relatively short length compared to most data transiRission signals, and each data signal.for portable unit is highly variable (reducing the possibility of a long series of continuous 1101s11 or fildste), these data transmission signals do not adopt readily to the advantages typically associated with the compression protocols.

Actually, maintaining the compression protocols in portable unit data transmission between modems may actually result in slower overall data transmission time since the time required (where the compression protocols are maintained) to compress the original signal, and re-expand the compressed signal often exceeds any time saved in sending and receiving a compressed signal between the sending and the receiving modems.

It has been found desirable (for the radio signal between radio portions 30 and 32) to utilize a non-licenseable radio frequency omnidirectional signal. This signal is preferably a spread spectral type of signal in the 300 MHz frequency band. This does not require an FCC site license and can provide an adequate communications range if the portable units are in close proximity to each other. It is also recognized that the portable units 16 may not be in close proximity to each other. In this case, a stronger radio frequency may be used for the first radio portion 30 and the second radio portion 32 (typically 460 to 470 MHz). When these higher frequencies are used, an FCC license is required. These frequency ranges are used for illustration purposes and are not intended to be limiting.

It is desirable that the land line bypass device 80 can be optionally connected between the communications controller 12 and the host portion 11. The function of this device is to permit the control unit 34 and the personal computer 64 to communicate via the land line 82 (typically existing telephone lines). The land line bypass device 80 includes the land line 82, a first phone jack 84, a second phone jack 86, a first jack wire 87, a first electrical switch 88, a second electrical switch 89, and a second jack wire 90. When the electrical switches 88 and 89 are in a first position (electrically connecting the cellular telephone 40 to the modem 35), all signals passing from the control unit 34 through the modem 35 will pass to the personal computer 64 utilizing the first and the second cellular telephone portions 40, 44 and the modem 60, and all signals passing from the personal computer 64 to the modems 35 will follow the reverse route. When the electric switches 88 and 89 are is in the second position (electrically connecting the modem 35 to the first phone jack 84), all signals passing from the control unit 34 through the modem 35 will pass to the personal computer via the first jack wire 87, the first phone jack 84, the land line 82, the second phone jack 86, the second jack wire 90 and modem 60, and all signals passing from the personal computer 64 to the modem 35 will follow the reverse route.

The advantages of the land line bypass device 80 configuration is that when both the control unit 34 and the personal computer 64 are in close proximity to a suitable land line, the electrical switches 88, 89 are switched to the second position and the more cost efficient land line method of signal transmission is used. Through the remainder of this application, the switches 88, 89 will be considered as being positioned in the first position. It is to be understood that the present system works equally well with the switches in the first and second positions.

Two progressions in which the present system typically follow are illustrated in Figs. 2 and 3. The Fig. 2 progression is utilized where the host portion 11 sends out an interrogation signal (via the communications controller 12) to the transceiver 14, polling the control unit 20 to monitor or control the operation of the portable unit 16 in some manner, using the D/A converter to translate the digital signal from the control unit 20 to the portable unit 16 and an A/D, converter to translate the analog signal from the portable unit 16 to the control unit 20. The control unit 20 will thereupon respond to the interrogation signal, and will send some type of response or affirmation signal to be received by the control unit 34 and/or the personal computer 64. 5 The Fig. 3 progression is utilized where the communications controller continually monitors some operational parameter of the portable unit 16. If one of the monitored operational parameters reaches an alarm or shutdown level, a digitalized signal will be sent to the control unit 20 of the communication controller 12. The control unit 20 will respond as programmed either by sending a signal to the portable unit 16, by transmitting the information to the host unit 11, or by more closely monitoring future and other related conditions of the portable unit 16.

Fig. 2 illustrates one type of progression which the control unit 34 of the communication controller portion 12 may utilize. The logic of Fig. 2 may be arranged in an interrupt loop which is run approximately each 25 milliseconds, depending upon the function and the operating parameters of the portable unit 16, as well as other design parameters. The progression includes five steps and two decisinn. The general function of the progression is to 25 permit the control unit 34 to determine (either by an internal decision or more commonly as dictated by the personal computer 64) which transceiver portion 14 should be polled, send the appropriate signal to poll that specific transceiver portion, receive the pertinent information from the polled transceiver and send affirmation of the correct response, or the desired data, back to the host portion 11. The first step in Fig. 2 is the Scan Cellular Phone Step 100 which scans for data information sent from the second cellular telephone unit 44 of the host portion 11 to the first cellular telephone unit 40, which would instruct the communication control unit 12 to poll one or more of the portable units for one or more types of operating parameters or functions. The Has A Data Request From The Host Portion Been Received And Store Decision 102 acts to repeatably perform Step 100 (in the millisecond range) until a signal from the personal computer 64 of the host portion 11 is received, then store the signal in a volatile memory portion 35a associated with the control unit 34. This ensures that any request for polling from the host portion 11 is received, and acted upon by the communication controller portion 12 as desired.

Any affirmative response to decision 102 results in a Determine Which Machine Data Is Requested From Step 104 being 25 performed, while a negative response results in a continual repeat of Step 100. Step 104 analyzes the data received from step 100 and registers the specific portable unit 16 whose transceiver portion 14 is to be polled. Since there may be as many as several hundred portable units 16 whose transceiver portion 14 responds to the same communication control portion 12, being able to accurately and quickly control specific portable unit(s) is vital. The instruction sent from the personal computer 64 to the control unit 34 in Step 100 and Decision 102 utilize the personal computer 64, the modem 60, the cellular telephone units 44, 40, a modem 35, and the control unit 34.

A Request Data From The Machine Step 106, a Is Data Received From Control Unit 20 Decision 108, a Send Data Top Host Via Cellular Phone Step 114 an Is Timeout Expired Decision 110, and a Send Error Message To Host Via Cellular Phone Step 112 combine to control transmissions from the communications controller 12 to the transceiver portion 14 in a half duplex manner (based upon the signal translated to the control unit 34 from the host portion 11 in steps 100 and 102), describing the desired instructions via data which it wishes the transceiver portion 14 to perform on the portable unit 16, and receiving any suitable data response from the transceiver portion 14 based upon those instructions. Step 106 sends a signal. from the control unit 34 to the specified control unit 20 utilizing modem 33; radio portions 32, 30; and modem 21. This signal (as are the other digital signals in this specification) is in standard sixteen bit ASCII format and contains a modified corresponding signal to those instructions sent from the personal computer 64 to the control unit 34 in Steps 100 and 102.

Decision 108 causes the control unit 34 to scan inputs from the modem 33 for any return digital signals from the transceiver portions 14 which relate to the signals sent in Step 106. Any Step 106 signal originates from the portable unit 16 and are translated to digital signal formed via the A/D converter lga. The signals which Decision 108 scans for can fall into two categories. The first category are response signals wherein Step 106 requests the control unit 20 to determine some operational parameter of the portable unit 16, and the signal received in Decision 108 and step 114 relates to the value of that operational parameter (speed of a compressor, engine temperature, rate of drilling of drill equipment, etc.). The second category of signals sent in step 106 are affirmation signals. wherein Step 106 requests the control unit 20 to perform some function (load and unload a compressor, shut down a compressor or some mining equipigent, control the speed of mining equipment or tool, etc.), and Decision 108 affirms that the function has been performed.

Decision 110 causes the control unit 34 to continually monitor the modem 33 for the time between the signals originating from the control unit 20 which corresponds to Step 106, and the reception of suitable data as illustrated by decision 108. Decision 110 ensures that a loop is performed for a predetermined period (the predetermined period should relate to a time in which a suitable response from Step 106 should be received, i.' e. a timeout period). If no suitable response is received and the timeout period has expired, step 112 causes an error signal to be transmitted back to the personal computer 64, which thereupon indicates that no suitable response has been received. If no response is received and the timeout period has not expired, then Step 106 is performed again, and another attempt is made to send the signal (stored in volatile memory 35a) from Decision 102 to the transceiver portion 14.

If the control unit 34 does receive a suitable response from the transceiver portion 14 corresponding to the signal sent in step 106 within the timeout period, then a Send Data To Host Via Cellular Phone Step 114 sends a signal (in a format,.similar to that illustrated in Fig. 4) via modem 35; cellular telephone portions 40, 44; and modem 60 to the personal computer 64. The personal computer 64 then may analyze, store or display the information as desired and preprogrammed.

Fig. 3 illustrates a loop in which the control unit 34 which performs an alternate type of progression from the Fig.

2 progression. The Fig. 2 progression functions by having the personal computer 64 control the operation and/or monitor specified operational parameters of the portable units 16 which depend from that personal computer 11. The Fig. 3 progression, by comparison, causes the control unit 34 to continually monitor desired operational parameters or operations of the portable units 20 which the control unit 34 is associated with. For a given portable unit, certain operational parameters may be controlled using the Fig. 2 logic, while other operational parameters may be controlled using the Fig. 3 logic.

The Fig. 3 logic is organized as an interrupt loop which originates from the control unit 34, and is transmitted to the control unit 20 each five minutes (or any desirable period).

This time period (which is preferably altered for machines of different sizes, performances and functions) permits a continual monitoring of the critical operating parameters at a sufficient interval to limit catastrophic failure while reducing energy consumption and heat production. The Set Machine Number To 1 Step 202 initially increments the machine number to the first machine in which polling is desired (in this case machine 1).

The two portions which poll the desired machine(s) are a Poll Machine Data Step 204 and a Is Machine In Alarm Shutdown Mode Decision 206. Step 204 sends a signal from control unit 34 to control unit 20 via modem 33, radio units 32 and 30, and modem 21 instructing the control unit 20 to determine some typically critical operational characteristic of the portable unit 20. After control unit 20 receives the signal from Step 204 a corresponding signal is sent to the portable unit 16 via the D/A converter, precipitating a return signal being sent from the portable unit (or a sensor associated therewith) via the AD converter 19b to the control unit 20. Decision 206 monitors for a digital return signal from modem 33, in response to the signal sent in Step 204, which indicates whether the portable unit 16 is in a shutdown or alarm state.

If the specific portable unit being polled is not in a shutdown or alarm state as determined by decision 206, an Increment Machine Number Step 208 will cause the machine which Steps 204, 208 and decision 206 are being performed on to be incremented.

If the specific portable unit 16 being polled is in a shutdown or alarm state as indicated by Decision 206, then a Save Machine Data Step 210; a Alert Host Portion Via Cellular Telephone Step 212; a Pass machine Data To Host Step 214, and an Increment Machine Number Step 216 are performed in progression. Step 210 stores the information received from Decision 206 in non-volatile memory (as described later) indicating that there was an alarm or shutdown condition, and what the values and/or conditions thereof are. Step 210 is not only useful in the transfer of this information, but also in analyzing the progression of values and/or conditions prior to some failure if such a failure occurs.

Step 212 alerts the personal computer 64 of the host portions 11, (utilizing modem 35, cellular telephone units 40 and 42, and modem 60) that some alarm or shutdown has occurred. Step 214 transfers all pertinent information digital data relating to the above alert and/or shutdown stored in control unit 34 to the personal computer 64 to be stored therein. In this manner, the human operator of the personal computer 64 can more precisely analyze what is causing the specific alarm or shutdown condition, and the human operator can interject within the loop either by calling the human user of the portable unit 16, or by triggering the control unit 34 to alter the operation of the portable unit 16 via the control unit 20 as shown in Fig. 2.

The personal computer 64 may either respond to the alarm or shutdown in an appropriate manner, or else an indication of the alarm or shutdown may be provided to the human operator of the personal computer in a suitablemanner. This response may be to alter some operational characteristic of the portable unit by a progression similar to that illustrated in Fig. 2 and previously described. Step 216 performs an identical function to step 208 (incrementing the machine number) as described previously and will not be detailed further here.

Data transmissions between the control units 20 and 34, or between the control unit 34 and the personal computer 64 of the host unit follows a digital data format as illustrated in Fig. 4, and organized in eight bit ASCII code. Each data format line includes six portions which are a Start Character Portion 250, a Machine Address Portion 252, a Command Portion 254, a Data Portion 256, a Cyclic Redundancy Check Portion 258 and a Carriage Return Portion 260.

The Start Character Portion 250 alerts whichever control unit 20, 34 or personal computer 64 is receiving the signal that the signal is about to be transmitted. The Machine Address Portion 252 states which portable unit(s) 16 this particular signal relates to. The Command Portion 254 contains the specific instructions, parameters etc. which the signal is conveying and relating to. The Data Portion 256 contains the specific values of the Command Portion instructions and/or parameters which either are desired to be obtained or have been achieved. The Cyclic Redundancy Check Portion 258 is a known device in computer transmission which permits parity checking of the prior portions 250, 252, 254 and 256 to ensure that the digitalized signal was properly transmitted and/or received. The Carriage Return Portion 260 acts as an end of transmission instruction indicating to the receiving control unit 20, 34 (or personal computer 64) to begin compiling and analyzing the signal.

Figure 5 illustrates the structure of the volatile memory units 25a, 35a; the non-volatile memory units 25b, 35b; and the program memory units 25c, 35b illustrated in Fig. 1. Each c>f the volatile memory units 25a, 35b are identical, as are each of the non-volatile memory units 25b, 35b and each of the program memory units 25c, 35c. The control units 20, 34 are also identical to each other and typically include an Intel 80C196 microcomputer (not shown). The control units 20, 34 (including the incorporated microcomputer) control the 5 accessing and retrieval of memory.

The first type of memory associated with the control units 20, 34 are the volatile memory units 25a, 35a which consists of a volatile RAM (Random Access Memory) and is used to store data and other variables (in digital format) associated with monitoring and control of the portable unit 16. Any signal from sensors (not illustrated) which are associated with the portable unit 16 is translated via the A/D converter to the control unit 20 so that it may appropriately be stored in the volatile memory units 25a, 25b. The control units 20 and 34 continually scans for the digital information. Alternately, commands may be generated from the personal computer 64 portion of the host portion 11, which are to be stored in the volatile memory units 25a, 35a. The type of commands which may be issued from the host portion include start or stop the portable unit, unload or load a compressor, and alter the speed of drilling equipment. The volatile memory units 25a, 35a contain 32K Bytes.

(32,000 Bytes) of memory. The volatile memory units 25 25a, 35a is not organized as a wrap around memory.

The second type of memory is the non-volatile memory units 25b, 35b which contain an Electrically Erasable Programmable Read Only Memory (EEPROM) which are used to store constants which may be altered during the lifetime of the portable unit, as well as constants of calibration which are associated with sensors associated with the portable units 16 (as originally installed). The non-volatile memory unit 25b only (and not the non-volatile memory unit 35b) contains a fault log of various shutdown conditions (not illustrated) as described below. Each of the non-volatile memory units 25b, 35b are SK Bytes long, and the fault log portion is the only portion of all of the memory units which is organized in a wrap around memory configuration.

The fault log portion of the non-volatile memory unit 25b can store up to 2500 events (an event being a shutdown or alarm condition in the portable unit) in non-volatile memory, and after the 2500th event is stored, the memory pointer goes to the first address and stores the new events in place of the original events. An example of an event would be a higher than normal temperature reading from a critical portion of the portable unit 16, or an unexpected rotational velocity of the portable unit. The event is stored in digital format, with the error code, and the time of the error being stored. During normal operation, the fault log is extracted from the control unit 20 memory on a periodic basis (preferably during routine maintenance). The fault log is preferably accessed locally at the transceiver portion 14 using a personal computer, but alternately may be extracted from the personal computer 64 located at the host portion 11 in a manner known in the art. A service person and/or troubleshooter can analyze the fault log portion of the EEPROM, and determine what may the cause of poor operation of the portable unit 16 and/or the transceiver portion 14.

Considering that there are so many 'storage locations in the EEPROM, it is unlikely that there will be more errors reported to the EEPROM than there is space in the EEPROM, but if this circumstance does occur, the EEPROM will "wrap-around" to write over the stored information in space 1. By the time that this wrap around function has occurred, there should be enough time between when the original data in any storage space was stored, and the time that the overwrite information is stored in the same storage space that the original information should be largely irrelevant in determining any fault in the operation of the present invention.

The third primary type of memory associated with each control unit 20, 34 is the program memory units 25c. 35c.

The program memory units 25c. 35c. consists of an EPROM (Electrically Programmable Read Only Memory). The EPROM contains 64K of non-wrap around memory and is used to store the program which the control units 20, 35 executes (summarized in Figs. 2 and 3). The program memory units 20, 34 also contains instructions utilized in booting procedures. The structure and function of a typical EPROM is well known in the art and will not be further detailed here.

The control units 20, 35 and their associated memory units function in the following general manner, if the Fig. 2 format is followed. The control unit 20 retrieves a command from control unit 34, and originated from the personal computer 64. The command is stored in the non-volatile memory unit 25b. The control unit runs the program from the program memory unit 25c using the data from the non-volatile memory unit 25b. (also possibly using constants from non-volatile memory unit 25b). The control unit 20 thereupon either performs a control function utilizing the D/A converter 19b, or retrieves appropriate data from the portable unit 16 via sensors and the A/D converter 19a to be stored in the volatile memory unit 25a. If data is retrieved, then the control unit will send the data information stored in the volatile memory unit 25a to be stored in the volatile memory unit 35a, and ultimately into the personal computer 64.

If the Fig 3 format is followed the control unit 20 will retrieve appropriate data, as indicated from the program memory, each period of time (typically each five minutes). The control unit 20 will thereupon receive digital information generated from sensors and the A/D converter 19a. If the value of the signals received therefrom exceed a predetermined limit as stored in the non-volatile memory unit 25b, then a digital signal indicating the error time and error code will be transmitted to the volatile memory unit 35a and the personal computer 64.

Fig. 5 illustrates the physical layout of the memory units associated with control unit 20 or 34 (both being identical) as illustrated in Fig. 1. The control unit 20 or 34 are both microprocessor based, as previously described. Address latches 300 latch the outgoing address from control unit 20 or 34 to the appropriate memory unit along a first bus (or set of busses) 306 which is configured to transmit data in a first direction only (left to right as illustrated in Fig. 5). A second bus 308 is configured to transmit data in both directions.

Address information being sent from the control unit 20 or 34 to the memory units is stored in the following manner.

The address latch 300 issues a command (based upon the command from the control unit 20 or 34) to a chip decode logic device 310 to enable the specific memory unit which provides the address of a specific memory location which the digital signal is to be applied to. The chip decode logic device 310 thereupon sends a signal directly to one of the memory units to enable the appropriate memory address. Finally, the data signal is transmitted from the latch 300 along the first bus 306 to the enabled memory unit, the enabled chip performs the desired function, and an appropriate response is returned along the second bus 308 to the control units 20, 34.

The present invention provides a simple and effective manner to determine control operation of and/or monitor operation of a plurality of portable units which are located remotely from a control or monitor location by effective transmission of data signals. The invention also permits the above functions while using only one cellular telephone line for a relatively large group of portable units, each portable unit containing a transceiver portions capable of sending and/or receiving data signals. Finally. the invention permits the portable units to be relocated about a work site without having to worry about land lines which previously became tangled and made this relocation difficult and slow.

An appropriate design consideration for the present invention relates to the transmission speed for various portions of the digital communication system 10. The quality of the data transmission signal varies considerably based upon where the portable unit 16 is positioned relative to the communications controller 12 and/or where the communications controller 12 is positioned relative to the host portion 11. The poorer the transmission quality of the digital signal, generally the slower the optimum rate of the transmission of the digital communication will be. ' Each set of modems (modems 60 and 35 being a first set while modems 21 and 33 are the second set) are capable of continual auto retrain which permits adjustment of the digital signal transmission speed based upon the digital signal quality.

Variations of transmission rate (Bits per Second) by auto retraining is especially important between the different sets of modems where the modems are positioned at different positions relative to each other, as in the present application of monitoring portable units. Similarly, variation of transmission rate by auto retraining is important between the first set of modems 35, 60 and the second set of modems 21, 33 since the two sets of modems receive a different type of signal (cellular telephone vs.

radio) as well as a different quality of signal (potentially intercontinental vs. local).

Logic behind the auto retrain portion is illustrated in Figure 6. A Set BPS Rate to. 2400 Step 350 sets of BPS Rate at the lowest rate which is normally used in this type of transmissions. In between each set of modems as previously characterized, the two communicating modems are characterized as an originating modem or an answering modem. The originating modem is a modem which sends an interrogation signal while the answering modem is the modem which receives the same interrogation signal. Using this nomenclature, a Send Message From Originating Modem at BPS Rate to Answering Modem Step 352 sends an interrogation signal to the answering modem, which the originating modem expects the answering modem to respond to. A Receive Answering Modem Message Step 354 receives a response message from the answering modem. Typically the interrogation message sends from the originating to the answering modem is identical to the response message received from the answering modem to the originating modem, therefore there is not any differences between the message sent by the originating modem and the message received by the originating modem. Under these circumstances, if the originating modem receives a different message than it sends, then the originating modem knows that the reception is poor.

In the present application, it is critical that there by 100 percent correspondence between the two signal, since digital information transfer is involved. An Is Originating Message Same As Received Message and Less Than Maximum Value 5 Decision 358 compa res these two messages. If the answer to Decision 358 is affirmative, then an Increment Value of BPS Connects Higher Value Step 360 is performed. Step 360 increments the BPS Rate to the next higher rate following the general progression of 2400 BPS, 4800 BPS, 7200 BPS, 9600 BPS, 14,400 BPS, and 19,200 BPS. (The rates are customary by current standards.) If the answer to Decision 358 is negative, then a Decrement Value of BPS and Send Primary Signal at Decremented BPS Value Step 362 is performed. Step 362 produces the BPS Rate to the highest rate at which there is a 100 percent correspondence between the originating and the answering messages. It is to be understood that many of other types of auto retrain programs, is a well known of the art, can be utilized and the present invention.

It is to be understood that auto retrain can also be intermittently utilized to protect against deteriorating 1 signals. A break portion (similar to Fig. 6) is interjected into the middle of a long message transmission sequence in a known.manner.

- 34 Considering the complexities of providing efficient and reliable transmissions between host portion 11, one or more communications controller 12, and one or more transceiver portions 14 associated with portable units 16, it should be evident that variation of transmission rate (Bits Per Second) by auto retraining is especially critical for data transmission utilising cellular telephones as related to the monitoring and control of portable units.

The directly wired serial communications (modem to computer) which are typically of a higher quality than other modem to modem connections. For this reason, the former is usually maintained at a higher rate than the latter. The above indicates several of the details which become especially critical when transforming digital information from a portable unit utilising a cellular telephone device and other associated links.

Claims (25)

CLAIMS:

1. A communication system comprising:

a portable unit; transceiving means, associated with the portable unit, for sending digital information via a first signal, the first signal being transmitted through free space; communication controller means for receiving the first signal, and transmitting a second signal which utilises a cellular telephone link, the second signal being based upon said first signal; and host means for receiving said second signal.

2. A system according to claim 1, wherein the digital information is based upon operating parameters of the portable unit.

3. A system according to claim 1 or 2, wherein the portable unit is a compressor.

4. A system according to claim 1, 2 or 3, wherein the first signal is a radio-frequency signal.

5. A system according to any one of the preceding claims, wherein the transceiving means is in close proximity to the communication controller means.

6. A system according to any one of the preceding claims, further comprising:

means for transmitting a third signal from the host means to the communication controller means utilising a cellular telephone link; and means for transmitting a fourth signal from the communication controller means to the transceiving means.

7. A system according to claim 6, wherein the third and the fourth signals are interrogation signals which result in a corresponding production of said first signal.

8. A system according to claim 6, wherein the third and fourth signals are response signals which result from, and correspond to, said second signal.

9. A system according to claim 6. 7 or 8, wherein the third and fourth signals have the capability of half-duplex operation.

10. A system according to any one of the preceding claims and comprising a plurality of said portable units, wherein each includes a said transceiving means, each transceiving means transmitting a said first signal to the communication controller means, the communications controller means thereby receiving a plurality of said first signals, and thereupon transmitting a plurality of said second signals to the host means, each of said second signals corresponding to one of said first signals.

11. A system according to claim 10, wherein the host means can identify specific portable units, from which each first signal which resulted in the generation of each second signal originated, in response to receiving the plurality of second signals.

12. A system according to claim 10 or 11 as appendant to any one of claims 1 to 5, further comprising:

means for transmitting a plurality of third signals from the host means to the communication controller means utilising a cellular telephone link; and means for transmitting a plurality of fourth signals from the communication controller means to the transceiving means associated with each portable unit, the third and fourth signals being responsive to the digital information of the first signals.

13. A system according to claim 12, wherein each transceiving means can identify which of said fourth signals, is being directed to the portable unit associated with that transceiver means, each fourth signal being based upon a specific third signal.

14. A system according to any one of the preceding claims, wherein the communication controller means is substantially stationary.

15. A system according to any one of the preceding claims, wherein the transceiver means further comprises a volatile memory.

16. A system according to any one of claims 1 to 14, wherein the transceiver means further comprises a non volatile memory.

17. A system according to claim 16, wherein the non volatile memory further comprises a fault log.

18. A system according to any one of claims 1 to 14# wherein the transceiver means further comprises a program memory.

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19. A system according to any one of the preceding claims, wherein the communication controller further comprises a volatile memory.

20. A system according to any one of claims 1 to 18.

wherein the communication controller further comprises a non-volatile memory.

21. A system according to any one of claims 1 to 18, wherein the communication controller further comprises a program memory.

22. A communication system comprising:

a portable unit; transceiving means, associated with the portable unit, for sending digital information via a first signal; communication controller means for receiving the first signal, and transmitting a second signal which utilises a cellular telephone link, the second signal being based upon said first signal, the first and the second signal capable of being transmitted at different transmission rates; and host means for receiving said second signal.

23. A system according to claim 22 and further comprising a set of modems associated with the communication controller and the host means, and auto retrain means for controlling a rate of transmission of said second signal based upon the quality of the second signal.

24. A system according to claim 22 and further comprising a set of modems associated with the communication controller and the transceiver means; and auto retrain means for _z controlling a rate of transmission of said first signal based upon the quality of the first signal.

25. A communication system, substantially as hereinbefore described with reference to the accompanying drawings.