WO1997030879A1

WO1997030879A1 - Remote monitoring system

Info

Publication number: WO1997030879A1
Application number: PCT/AU1997/000097
Authority: WO
Inventors: Herbert Gregory Greber; Donald Butterfield; Edward Allum
Original assignee: Queensland Rail
Priority date: 1996-02-23
Filing date: 1997-02-21
Publication date: 1997-08-28
Also published as: ID16203A; ZA971482B; AUPN828396A0; TW327222B

Abstract

A remote monitoring system for remote monitoring of field equipment. The system has one or more sender units (50) for monitoring field equipment and transmitting a multiword message to a receiver unit (51). The receiver unit being capable of communicating with a plurality of sender units (50) and providing for telemetric communication with a control station, outputs information to a computer (56, 57), a printer (52), a pager (55) and generates alarm signals.

Description

REMOTE MONITORING SYSTEM

THIS INVENTION relates to a system for the remote monitoring of field equipment. In particular, the invention relates to a system for the remote monitoring of railway field equipment such as level crossings, weather stations and dragging equipment detectors, in a continuous manner.

Items of ancillary equipment comprising a railway system can be located many kilometres, even hundreds of kilometres, from maintenance or operating centres. Such equipment is invariably automated. Constant monitoring of equipment such as level crossing equipment is required in respect of the operational status of the equipment and to provide warning of failures or potential failures. Any warning must be in sufficient time to allow any railway system control centre to take appropriate precautionary action and to advise maintenance staff. Similarly, data from monitoring equipment such as weather or flood monitoring stations and dragging equipment detectors need to be continuously received so that appropriate precautionary action can be taken.

Efficient and safe operation of a railway system is dependant on immediate action in respect of equipment failure or hazardous environmental conditions such as flooding. In addition to equipment and environmental conditions being continuously monitored, the monitoring must be such that an event requiring action is brought to the attention of maintenance or operational personnel.

It is an object of the present invention to provide a remote monitoring system which allows for the continuous monitoring of field equipment and comprises a plurality of warning or output signal modalities. According to a broad format, the invention provides a remote monitoring system comprising: at least one sender unit for monitoring field equipment, said sender unit being capable of transmitting a multi word message; a receiver unit linked to said at least one sender unit and capable of individual communication with each of a plurality of sender units, said receiver unit further including interfaces for: ι) telemetnc communication with a control centre n) on-line communication with at least one computer, m) on-line communication with a printer, and iv) on-line communication with a paging wherein a defined event message received by said receiver unit generates an alarm signal which is communicated to said control centre, said at least one remote computer, said printer, or said pager

The system described in the preceding paragraph is particularly suited for the continuous monitoring of railway system equipment Such equipment includes level crossings, weather monitoring stations and dragging equipment detectors Weather monitoring stations are typically employed to monitor flooding, rail temperature or rainfall

The linkage between a sender unit and the receiving unit is typically by transmission line or by radio Radio linkage is particularly preferred A receiving unit typically receives data from up to 63 sender units

The receiving unit advantageously includes a display such as an LED display so that incoming messages can be visually monitored Any display preferably also has in conjunction therewith an alarm responsive to a defined event message Defined events which generate an alarm signal in connection with a railway system include low battery voltage, charger fail, train speed, XSR out of correspondence, light operating for excessive time, lamps blown or not flashing, flood water at or above rail level, rail temperature above a certain level, and, rainfall above a certain level The following description gives examples of message configurations and preferred unit configuration and operation

The following abbreviations are used in the drawing and hereafter

CTC centralised traffic control

FCR flashing control relay FEO flashing light resistor

IE infrastructure engineer

PC personal computer RX receiving unit

TX sender unit

XD_nR crossing down relay

XSR crossing stick relay SENDER UNIT

The sender unit is the unit which monitors the field equipment and reports back to a receiver unit by the transmission of a multi word coded message either by direct hard wire or by radio link The message is Keyed

Frequency Shift 2 1 kHz tone, (± 300 Hz) -14 db into 300 ohms transmission at 600 baud Bridging impedance to line is 8 kohms

The transmission is a multi word message formatted as follows WORD ONE START FRAME - This is an 8 bit word using bit 7 for parity checking WORD TWO ADDRESS COMPLIMENT - This is an 8 bit word using bits 0 - 5 for coding, 6 is a bit 15 complement and bit 7 for parity checking WORD THREE ADDRESS - This is an 8 bit word using bits 0 - 5 for coding, 6 is bit 15 and bit 7 for parity checking WORD FOUR DATA - This is an 8 bit word using bits 8 - 14 for inputs and bit 7 for parity checking

WORD SIX This is an 8 bit word using bits 0 - 6 to indicate relay outputs the field units current state of the output relays and bit 7 for parity checking. WORD SEVEN CHECK SUM This is an 8 bit word using bit 7 for parity checking Each message lasts for approximately 100 milliseconds plus pre- data delay to allow the radio links to establish The unit waits until the line is clear and then after a further period of 10 seconds it attempts to transmit the message

The message is sent in the following sequence until an acknowledgment message is received a) initially four transmissions at 10 - 24 second intervals, b) then three transmissions at 10 - 24 second intervals after a further five to six minutes has elapsed, c) then one transmission approximately every 30 minutes or at five to six minute intervals for bit 15 = 1 (Low Voltage) until acknowledgment message is received. The sender unit has a standard configuration for alarms which must be maintained as the Receiver unit interprets the bits received from a standard bit map. An alterative message sequence is as follows- a) Initially four transmissions at eight second intervals, b) then two transmissions at eight second intervals every fifteen minutes for inputs 2, 3 and 4 or two transmissions at eight second intervals every five minutes for input 1 , c) continuously at eight second intervals until acknowledged for Dragging Equipment Detectors The Sender unit has a standard configuration for alarms which must be maintained as the Receiver unit interprets the bits received from a standard bit map. The bit maps for the various applications are as follows

LEVEL CROSSINGS

BIT ONE- XD_nR

BIT TWO: Lights flashing

BIT THREE: XSR Energised BIT FOUR. Mams Supply

BIT FIVE Charger Failed

BIT SIX "B" Track.

BIT SEVEN Train speed (insufficient warning time)

BIT EIGHT- Lamps blown or not flashing (FEO 1 ) BIT NINE Lamps blown or not flashing (FEO 2)

BIT TEN Lamps blown or not flashing (FEO 3)

BIT ELEVEN Lamps blown or not flashing (FEO 4) BIT TWELVE Lamps blown or not flashing (FEO 5) BIT THIRTEEN. Lamps blown or not flashing (FEO 6 or 7) BIT FOURTEEN XSR or boom fall time sequence failure BIT FIFTEEN- Low Battery Voltage

WEATHER STATION SITES BIT 1 : Alarm - Rail Temperature above 58^° C

Recovery - Rail Temperature falling 55^° C. BIT 2' Alarm - Rail Temperature above 62^° C Recovery - Rail Temperature falling 59^° C.

BIT 3 Alarm - Rail Temperature above 66^° C

Recovery - Rail Temperature falling 63^° C. BIT 4' Alarm - Peak Summer temperature of more than 58°C BIT 5 Alarm - Rainfall exceeding 100mm/hr Recovery - Rainfall easing 50mm/hr

BIT 6. Alarm - Rainfall in 1 hr greater than 100mm

Recovery - Rainfall in 1 hr less than 25mm. BIT 7 Alarm - Temperature sensor failure.

Recovery - Temperature sensor OK IT 8. Alarm - Flood sensor not working

Recovery - Flood sensor working IT 9. Alarm - Flood level rising at -1.0 Metres

Recovery - Flood level falling at -1.2 Metres IT 10: Alarm - Flood level rising at -0.4 Metres. Recovery - Flood level falling at -0 6 Metres IT 1 1 Alarm - Flood level rising at -0 1 Metres

Recovery - Flood level falling at 0.2 Metres IT 12 Alarm - Flood level rising at Rail Level

Recovery - Flood level falling -0 1 Metres IT 13 Alarm - Flood level rising at +0 2 Metres

Recovery - Flood level falling at Rail Level IT 14 Alarm - Flood level rising at +0 5 Metres Recovery - Flood level falling at +0 2 Metres BIT 15 Alarm - Battery voltage below 10 5 Volts

Recovery - Battery voltage above 12 Volts The sender unit is programmed to respond to inputs as follows LEVEL CROSSINGS

BIT ONE The Sender Unit monitors a boom arm horizontal relay

XD_nR normally closed contact and if this contact is broken for longer than 20 minutes an alarm is raised back to the Receiver Unit A recovery message is sent when the crossing down relay front contact is made BIT TWO The sender unit monitors the state of a front contact of the Flashing Control Relay (FCR) If this contact is broken for more than twenty (20) minutes an alarm is sent to the receiver unit

A recovery message is sent when the Flashing Control relay front contact is made BIT THREE

The sender unit monitors the state of a back contact of the Crossing Stick Relays (XSR) If any of the XSR's energise and remain energised for a period of time in excess of twenty (20) minutes when the lights are not flashing, an alarm is sent to the receiver unit A recovery message is sent when all the Crossing Stick Relays are de-energised

BIT FOUR

The sender unit monitors the 240 Volt supply via a 12 Volt AC plug pack If the 12 Volt AC supply is interrupted for more than 10 hours an alarm is sent to the receiver unit

A recovery message is sent once the 12 Volt AC supply has been restored uninterrupted for a one minute period BIT FIVE The sender unit monitors a front contact of the Auto

Regulator Charge Fail Relay If this contact breaks with the 240 Volt supply available for a period of time in excess of 15 minutes an alarm is sent to the receiver

A recovery message is sent once the Charge Fail Relay has re-energised for 5 minutes

BIT SIX The Sender Unit monitors a front contact of the Crossing

(road) Track Relay. The bit is sent to the receiver unit if the track is occupied for longer than 10 minutes but no alarm is raised Its purpose is to identify the actual crossing of a train. BIT SEVEN

The Sender Unit monitors the sequence of events which occur on its inputs to determine whether a train passage over the crossing has occurred If it is determined that a train passage has taken place the Sender Unit assesses whether the approach warning time to motorists is over 15 seconds. If this warning time is less than 15 seconds, an alarm is sent to the Receiver Unit and if booms installed they must be indicating horizontal when the train enters the crossing BITS EIGHT - FOURTEEN

The Sender Unit monitors up to seven flashing light resistors for voltage drop between 0 18 Volts and 3 2

Volts, the rate at which the voltage is switched and the state of the Flasher Control Relay Alarms are sent to the Receiver Unit if a) The Resistor voltage varies by more than 20% of the datum level for 6 seconds b) The Flash rate is outside the range of 25-60 flashes per minute c) There is a voltage drop across a flashing light resistor when the Flasher Control Relay is energised. This alarm is raised after 5 minutes or after 4 seconds if the Flasher Control Relay has just energised. d) The calibration switch is performed by operating the push button whilst the lights are on The unit stores the normal values for reference

Recovery messages are sent when these levels return to within the units datum levels.

BIT FIFTEEN:

The Sender Unit monitors its own input voltage. When this voltage falls below 10 Volts an alarm bit is sent back to the Receiver Unit A recovery message is sent after the voltage rises above

12 Volts WEATHER STATION AND DRAGGING EQUIPMENT SITES: BIT 15 The sender unit monitors its own input voltage When this voltage falls below 10 Volts or over 15 volts an alarm bit is sent back to the receiver unit.

A recovery message is sent after the voltage rises above 12 Volts and below 14 volts. BITS 1 TO 14

All inputs are monitored and alarm/recovery messages are sent to the receiver unit when the alarm/recovery levels are reached.

The messages are sent after a delay of 3 minutes for flood alarms (to prevent false alarms due to debris) and immediately the event occurs for temperature and rain fall

The sender unit is a multiplexed unit capable of handling fifteen indication bits and seven output bits The sender unit can accept up to seven digital indication bits, using 10,000 Volt opto couplers which provide field isolation and acceptance of AC or DC input voltages from 5 Volts up to 70 Volts (Normally 12 Volt DC) or seven analogue inputs from between 0 to 5 Volts The Unit is programmed by an 8K eprom to allow flexible computation of data and apply any logic required for alarm inputs before transmission. This eprom also carries out averaging of analogue inputs before storage to the on board memory. The unit is provided with a watch dog circuit to ensure correct program operation The unit has an 8K memory for holding an event history of changes of state at the inputs Data stored in the memory can be down loaded to the receiver unit directly on request. Each change of state is logged down to a minimum of one second time intervals provided by the on board timer However, actual time and date stamps are provided by the receiver unit to ensure exact time relationship between all sites

A maintenance timer is provided to prevent alarms being sent while maintenance is being carried out. This timer is activated by depressing a push button in the control box which starts a 60 minute alarm free period The timer does not need to be cancelled but can be by holding the button in, as normal operation is resumed after 60 minutes The LED on the front of the sender blinks while the timer is running. RECEIVER UNIT

The receiver unit is a micro processor based unit which can monitor up to sixty three different field stations. The unit has three bit tables permanently installed in its software and is capable of accepting a further three tables which are input from the CPU interface These tables relate to the alarm bit allocations for level crossings, weather stations an dragging equipment detectors

The Receiver unit communicates with its field units using a five word message which is structured as follows-

WORD ONE START FRAME - This is an 8 bit word using bit 7 for parity checking WORD TWO ADDRESS - This is an 8 bit word using bits 0 - 5 for coding, bit 6 for low voltage (bit 15) and bit 7 for parity checking WORD THREE ADDRESS - complement and low voltage complement WORD FOUR DATA - This is an 8 bit word using bits 0 - 6 to acknowledge inputs bits 8 - 14 data and bit 7 for parity checking WORD FIVE DATA - This is an 8 bit word using bits 0 - 6 for acknowledging the current status of the field unit bits 1 - 7, and bit 7 for parity checking On receipt of a field message the receiver unit will acknowledge on the line from which the transmission was received once for every message received The acknowledgment transmission by the receiver unit is a keyed 2 kHz tone of 14db into 300 ohms and a baud rate of 600 baud

The Receiver Unit of a level crossing remote monitoring system processes the message as follows

ONE The new change of state is updated on the LED panel display for future integration

TWO The new change alarm is transmitted to a CTC computer or dial up to dark territory controllers

The CTC computer raises a Prompt on the CTC controllers panel The controller is required to notify the relative maintenance staff of the alarm raised

THREE A pager message is transmitted to the responsible maintenance staff informing them of the event

FOUR The new change of state is sent to a printer port and is printed out In conjunction with this an alarm is raised in the office where the printer is located This alarm will continue to sound until cancelled FIVE The new change of state is sent to the PC interfaced with the receiver unit The Receiver Unit will not initiate all four of the above steps unless the change of state contains an alarm status which is recognised by a "^*" at the start of the message Where the "^*" is not present the receiver unit carries out the LED update, sends the change to the local computer interface and to the printer, but no audible alarm is initiated and no transmission is made to the CTC controller or pager

Processing of the message by the Receiver Unit of a weather stations system is as follows-

ONE The change of state is updated on the LED panel display for future integration TWO The change of state is sent to the Train Controllers panel via a dial up modem link in Dark Territory, or to the CTC computer either direct through a communications port

THREE The change of state is sent to the Infrastructure Engineer via a dial up modem link through a pager service The pager will display the alarm state for the site concerned FOUR The change of state is sent to the Infrastructure Engineers computer using a dial up modem

The receiver unit will not initiate all four of the above steps unless the change contains an alarm state which is recognised by a

"^*" at the start of the message Where the "^*" is not present the receiver unit carries out the LED update only The alarms sent to Dark Territory controllers is configured in a separate table

When an event history is required from a field station, the receiver unit will request the last forty-four changes of state at the field sender unit

The history is printed out using the bit change text messages contained in the Table for the relative site The receiver unit also adds the date and time stamps required for the message

The receiver unit can also obtain a full history of 770 events from the field station Due to time taken to obtain a full report back from the sender unit these reports are transmitted at a specified time when the system usage is minimal This report contains the sites text messages and is time and date stamped by the receiver unit

The receiver unit polls the individual sender units once every day after midnight If a sender unit fails to transmit a reply the Station OK LED on the LED panel is turned off and a message is sent to the printer Sender units can be checked at any time by request to prove the communication link and the operation of the unit

Alarms are typically identified in four ways (L E D indications, controller prompts, paging the Infrastructure Engineer and updating the

Infrastructure Engineers Computer) which reduces the possibility of an alarm going undetected To provide added security, the sender unit will keep trying to raise alarms until they are acknowledged by the receiver unit

So that the invention may be better understood, a monitoring system will now be exemplified with reference to the drawings briefly described hereunder

FIGURE 1 is a block diagram of a transmitter or sender unit according to an embodiment

FIGURES 2A and 2B show a block diagram of a receiver unit according to an embodiment of the invention,

FIGURE 3 is a detailed block diagram of the sender unit of Figure 1 ,

FIGURE 4 is a detailed block diagram of the receiver unit of Figure 2, FIGURE 5 is a further detailed block diagram of part of the receiver unit of Figure 4,

FIGURE 6 is a detailed block diagram of receiver modem configurations in the receiver unit,

FIGURE 7 is a detailed receiver block diagram, FIGURES 8A, B and C show a detailed circuit diagram of part of the sender unit of Figure 1 ,

F IGURE 9 is a detailed circuit diagram of a digital input circuit of the sender unit,

FIGURE 10 is a detailed circuit diagram of an analog input circuit of the sender unit,

FIGURE 1 1 is a detailed relay output circuit of the sender unit, FIGURE 12 is a detailed display circuit of the sender unit,

FIGURES 13A and B show a detailed circuit of part of the receiver unit,

FIGURES 14A, B and C show a further detailed circuit of part of the receiver unit, FIGURE 15 shows a further detailed circuit of part of a receiver unit,

FIGURES 16A, B and C show a detailed circuit diagram of connection circuitry for modems in the receiver unit,

FIGURE 17 is a detailed circuit diagram of a modem interface module which is included in the receiver unit, FIGURES 18A and B show a detailed circuit diagram of a serial driver array circuit

FIGURES 19A and B show a detailed circuit diagram of a modem connection circuit,

FIGURES 20A and B show a detailed circuit diagram of an auxiliary relay circuit, and,

FIGURE 21 is a detailed circuit diagram of an alarm output driver module

Figure 1 shows a block diagram of a transmitter or sender unit The unit has a CPU/modem module 30 with the modem providing its output to a transmission link such as a line, voice frequency link or a radio link The module 30 receives digital inputs from block 31 and analog inputs from block 32 A display 33 is coupled to module 30 to provide a visual indication of the status of the sender unit A plurality of similarly constructed sender units may be present in a system of the invention Figures 2A and B show a block diagram of a receiver unit for receiving and processing signals received from a plurality of sender units like that shown in Figure 1 The receiver unit has a central processor unit CPU 35 to which is coupled a modem bank 36 for coupling signals received from the sender units to the CPU 35 The bank 36 also allows control and acknowledge signals to be sent to the sender unit

The CPU 35 provides control signals to an alarm output module 37 so that alarm conditions detected by the system may be displayed and reported A switchbank 38 is coupled to the CPU 35 Display 39 indicates the status of the various received signals supplied to the CPU 35 A power supply including a DC/DC converter 40 is shown to the left of CPU 35 in Figure 2 Figure 3 shows a detailed block diagram of the sender unit of

Figure 1 Analog inputs are supplied to A/D converter 41 whilst digital inputs are applied to opto isolator/buffer module 42 The CPU 30 has ROM (or EPROM) and RAM memory modules 43, 44 A watchdog timer 45 periodically checks for proper operation of the CPU 30 Status display 33 in this instance is a LED display Control relay latch and driver module 46 is coupled to CPU 35 Modem 47 allows CPU 30 to transmit signals to a receiver unit

Figure 4 shows a detailed block diagram of a receiver unit and eight separate sender units 50 These units 50 transmit their signals in any suitable fashion such as, for example, over a voice frequency link, radio link or cable link The receiver unit has a main block 51 which receives eight inputs and provides 64 relay alarm outputs, controls a printer 52 and monitor 53, provides a control signal for a dial up modem 54 to operate pager 55 and sends signals to two computer workstations 56, 57 Block 51 also provides for control of CTC modem 54a for transmitting information to a Centralised Traffic control location Workstations 56 and 57 allow remote monitoring of conditions detected by the receiver

Figure 5 is a further block diagram of part of a receiver This block diagram shows that the receiver has a CPU 35 whose function is monitored by a watchdog timer 45 Outputs 0, 1 from the CPU 35 are employed to poll the display and the relay control decoder 60 Decoder 60 controls the 8 bit latches 61 Display 62 is controlled by drivers 63 and latch 64 Latch 64 also controls the 8 bit latches 61 Display select switches 65 correspond to single pole switch S1 and the switchbank 38 shown in Figure 2B The single pole switch, when in the position shown in Figure 2 allows signals from a sender unit to be displayed by the display When the switch is in the other position, the receiver may be used to send control signals to the sender units The switchbank of Figure 2 functions to supply signals from a selected 16 sites at which sender units are located to allow that group of 16 to be displayed Different switching combinations possible by the switch bank allows the display to selectively display different groups of signals from other groups of 16 sites

In Figure 5, the latches 61 control alarm relays The CPU 35 also provides a station alarm output and allows that alarm to be cancelled

The system includes a plurality of modems associated with the receiver unit As shown in Figure 6, eight such modem lines are present Figure 2 shows eight modem lines coupled to the CPU 35 These eight modems each provide outputs as shown which allow signals from the transmission link to be coupled to the CPU data bus as shown

Figure 7 shows detail of a receiver unit CPU 35 is coupled via an 8 bit bus to a plurality of ports Asynchronous port 70 allows the eight modems of Figure 5 to be coupled to the CPU Asynchronous port 71 allows the printer 52 and VDU or command screen 53 (see Figure 4) to be connected to the CPU 35 Asynchronous port 72 allows dial-up modem 54 (see Figure 4) to be connected to the CPU Synchronous port 73 allows the Centralised Traffic Control (CTC) modem (see Figure 4) to be connected to the CPU Each of the ports 71 , 72, 73 have RS232 drivers coupled to them A display and relay alarm port 74 is coupled to the 8 bit bus

Figures 8A, B and C show greater detail of a sender unit The unit has a CPU 30 coupled to a latch U21 and an address decoder U22 A further latch U26 allows CPU 30 to provide output signals for a purpose described below Connector JP13 allows the CPU 30 to receive digital input signals and to output signals to the display T ransistor Q4 and associated components function as a watch dog timer which monitors the operation of CPU 30 and is able to reset CPU 30 if required ROM (or EPROM) memory U23 and RAM memory U25 are coupled to CPU 30

Inputs ANO to AN7 are for analog input signals An A/D converter U24 receives these signals and applies them to the CPU 30

Figure 9 shows a digital input circuit Connector J19 applies digital signals to OPTO isolators, only one U27 of which is shown Schmidt triggers couple the output of the OPTO isolators to connector JP14 which in turn is coupled to connector JP13 in Figure 8C and to connector JP15 in Figure 12 Seven OPTO isolator circuits extend between connectors J19 and UP14 but only one has been shown in complete detail in this figure The remaining six of these circuits are identical to the one shown and are represented diagrammatically by block B1

Figure 10 shows an analog input circuit Connector J20 receives analog inputs and each one of seven of these inputs is filtered in a respective one of the seven filter networks One of the analog inputs is not filtered but is simply voltage divided and made available as ANO This allows the +12V battery voltage to be monitored as one of the analog inputs As mentioned, Figure 10 has seven filter circuits identical to the three illustrated extending between connector J20 and providing their outputs at terminals AN1 , AN2 and AN7 The four filter circuits are identical to the ones shown and are represented diagrammatically by block B2

Figure 1 1 shows a relay output control circuit which may form part of a sender unit The inputs RLY0 to RLY6 are derived from the terminals DO to D6 provided by latch U26 in Figure 8 These inputs control respective relays RLY1 to RLY7 for switching associated contacts to allow a sender unit to switch equipment at the site where the sender unit is located Relay outputs are available at connector J21 Only one of the relay circuits is shown in detail The remaining six are shown diagrammatically by block B2

Figure 12 shows detail of a status display circuit Connector JP15 is coupled to connector JP13 in Figure 8 Counter U28 controls latching of latches U29 and U30 which allow CPU 30 (see Figure 8) to activate an LED display consisting of diodes LED1 to LED15 These LED s provide the display 32 shown in Figure 1

Figures 13A, B and C show more detail of a receiver unit CPU U1 (or 35 as it is annotated in Figure 2) has ROM (or

EPROM) memory U2 and RAM memory U3 coupled to it Counter U4 and crystal XTAL1 provide a clock for controlling modem operation for the modems associated with the receiver. Data bus D (0-7) extending from the CPU U1 is coupled to the memory U2 and U3 and to other parts of the receiver unit

Figures 14A, B and C show a further detailed circuit diagram of part of a receiver unit The data bus D (0-7) from Figures 13A, B and C is coupled to a port interface circuit U5 Watchdog timer consisting of schmidt triggers U7A&B and other components provide a reset signal for CPU U1 in Figure 13 Switchbank J5 and switch J6 (or 38 and S1 as annotated in Figure 2B) are coupled to the port interface circuit U5 Drivers U7 and U8 extend between circuit U5 and connector JP2 to which a display is connected Driver U9 is located between circuit U5 and connector JP3 to which alarm outputs are supplied Driver U6 is connected between connector JP1 and the circuit U5 and supplies signals for operating a display

Figure 15 shows data bus DBUS coupled to a driver U12 Address signals are coupled to a driver U13 and directly to four connectors Z1 as shown Block B4 shows diagrammatically the other three connectors Z1 Modems (eight in number) are connected to these connectors with two per connector

Figures 16A, B and C show a port configuration for the receiver unit Port J8 is a printer serial port for printer 52 in Figure 4 Port J9 is a VDU serial port for the command screen 53 in Figure 4 Port J 10 is an auxiliary serial port to which the dial up modem 54 in Figure 4 is connected The last port J 1 1 provides a synchronous serial port to which the centralised traffic control modem 54a in Figure 4 is connected The connector Z2 A-B of Figure 16 connects to connector Z6 A-B in Figure 18 while connector Z3 is coupled to connector Z5-B in Figure 18 Address signals are applied to the logic circuit consisting of three inverters and two NAND gates and the final inverter conveys the signal to connector Z3 In Figure 17, connector Z4 is coupled to Z1 in Figure 15 Four circuits like that shown in Figure 17 are employed in the receiver unit - one for each of three connectors in block B4 corresponding to connector Z1 in Figure 15 Modem port circuits (ASCI drivers) U14 and U15 are located between connector Z4 and JP4 Two modems are connected to JP4 The circuit of Figure 17 is a modem interface module

Figures 18A and B show a serial peripheral driver array Three drivers U16, U17 and U18 extend between connectors Z5 - A/B and Z6 - A/B

Figures 19A and B show connectors JP7 to JP1 1 and terminals to which modems are connected In these figures block B5 shows diagrammatically the additional modem terminal configurations for the further four modems not shown in detail in the figures Connectors JP7 to Jp11 connect to respective connectors JP4 in Figure 17 Connector J12 to J 14 allow the modems to be connected to a communication link such as a voice frequency or radio link

Figures 20A and B show an auxiliary relay circuit of the receiver unit Connector J12 extends to connector JP3 in Figure 14 and allows alarm signals to be coupled to the relay circuit of Figure 20 Relay modules M1 and M2 are shown in detail and provide terminals to which a relay driver module (see Figure 21) may be connected Blocks B6, B7 and B8 each shown diagrammatically two further relay modules identical to the two modules M1 and M2 shown in detail These modules provide output COM and ALM1 -8 for operating alarms

Connectors J16, J17 and J18 may be coupled to a cable radio link or other link for conveying alarm signals to a remote location

Figure 21 shows a detailed circuit diagram of a decoder/driver module Eight such modules are present in the receiver unit of the invention Each module receives inputs CLR RDO-7 from CPU U1 in Figure 13 Latch U9 couples these signals to eight transistor/relay control circuits, of which only one is shown The others are configured in a like fashion and are shown diagrammatically by block B10 The transistor controls a relay and contacts as shown The module provides outputs COM and ALM1-8 signals

The remote monitoring system monitors or controls equipment which by nature is infrequent in its use The system exchanges data between the sender units and the receiver unit on a change of state basis That is, the receiver unit does not continually poll the sender units This allows the communication link or bearer to be shaved with existing services such as a voice radio link

The capacity of the system is limited to 63 remote sender units per receiver unit The receiver unit has 8 modem inputs and the 63 sender units can be on any of these 8 lines with no more than 16 sender units on any one modem line

Alarm signals at the sender unit pass through software timers in the computer which forms part of the unit before transmission to the receiver unit Timeouts can be configured for 0 to 1 and 1 to 0 state change from 0 sec to 18 hours in 1 sec steps

Upon receipt of a change of state at the receiver unit, the data is displayed in the receiver unit display The display is 16 addresses wide, switchable between address groups As well as the 14 external indication bits the status of the 12 volt supply to the sender unit is indicated The receiver unit sends a printout to the printer and the display at the receiver unit upon receipt of a change of address from the sender unit The auxiliary RS232 port is used to send information to a pager and remote computers via dialup modems The Sync data port communicates with a centralised traffic control (CTC) computer The ROM memory is provided by EPROM chips which store all configurations so that if a system fails, these chips may be transferred to a replacement system All RAM memory is non-volatile and has battery backup for which power is turned off

SENDER UNIT PROTOCOL

In each sender unit transmission time is 150mS plus link opening time The carrier detect input must be free for 10 sec before a transmission will be sent or if delayed for 15 minutes the transmission will be sent regardless

All sender units are tested by an all station poll once per day All transmissions from the sender units are acknowledged by the receiver unit irrespective of a carrier detect signal at the receiver unit All other transmissions from the receiver unit must have a carrier detect signal free If carrier detect signal is busy for more than 15 minutes without any breaks the receiver unit will ignore the busy input for that corns line unit a break of greater than 10 sec is detected

If the link to the receiver unit is not operating for some reason, the sender unit will continue to send until a reply is received The first four transmissions are sent at 10-24 sec spacings, dependent on address, then a 5-6 mm break, then three more tries at 10-24 sec If there is still no acknowledgment, a 30-31 m break occurs followed by one transmission is repeated until the link is re-established The receiver unit monitors transmission from sender units and if more than 16 transmissions are received in any 24 hour period from one sender unit an "excessive transmission" message is printed for that address The counters are periodically reset

Alarm signals will always be processed by the receiver unit once received even if a fault prevents the sender unit receiving the acknowledgment from the receiver unit

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS 1 A remote monitoring system comprising at least one sender unit for monitoring field equipment at a remote location, said sender unit being capable of transmitting a multi word message, a receiver unit linked to said at least one sender unit and capable of individual communication with each of a plurality of sender units, said receiver unit further including interfaces for i) telemetnc communication with a control centre ii) on-line communication with at least one computer in) on-line communication with a printer, and iv) on-line communication with a pager, wherein a defined event message received by the receiver unit generates an alarm which is communicated to said control centre, said at least one more computer, said printer or said pager 2 The remote monitoring system of claim 1 wherein the or each sender unit includes a digital input circuit, an analog input circuit and a status display, a computer coupled to the circuits and the display for providing the message for transmission to the receiver unit

3 The remote monitoring system of claim 2 wherein the sender unit includes a modem for transmitting the message from the sender unit to the receiver unit

4 The remote monitoring system of claim 2 or 3 wherein the message from the sender unit is transmitted to the receiver unit by a voice frequency link, radio link or a direct cable or optic fibre link 5 The remote monitoring system of claim 2 wherein the sender unit includes an interface circuit coupled to the computer and a relay output module controlled by the interface circuit whereby control signals sent from the receiver unit may control the relay module at the sender unit for controlling equipment associated with the field equipment being monitored 6 The remote monitoring system of claim 5 wherein the interface circuit is a latch and the input to the latch is coupled to the display and digital input circuit 7 The remote monitoring system of claim 2 wherein the sender unit includes an analog to digital converter in the analog input circuit

8 The remote monitoring system of claim 7 wherein the analog input circuit includes a voltage divider and a plurality of filter circuits for receiving analog inputs and for supplying filtered analog signals and a voltage divided analog signal to the analog to digital converter

9 The remote monitoring system of claim 2 wherein the digital input circuit includes a plurality of opto couplers for isolating digital signals from the computer in the sender unit 10 The remote monitoring system of claim 1 wherein the receiver unit includes a CPU and ROM and RAM memory

1 1 The remote monitoring system of claim 10 wherein the receiver unit includes, coupled to the CPU a display, alarm output means, a plurality of modems and display select switches for controlling the mode of operation of the display

12 The remote monitoring system of claim 10 wherein the receiver unit has eight modems

13 The remote monitoring system of claim 12 wherein the receiver unit has a plurality of ports for the interfaces for connection to the display, for connection to the eight modems, for connection to an auxiliary dial up modem, and for connection to a CTC modem

14 The remote monitoring system of claim 13 wherein the dial up modem is connected to the remote computer

15 The remote monitoring system of claim 13 wherein some of the ports are asynchronous ports and some of the ports are synchronous ports

16 The remote monitoring system of claim 1 1 wherein the receiver unit includes an alarm circuit for providing an audible alarm

1 7 The remote monitoring system of claim 14 wherein the receiver unit includes a serial port driver circuit for providing the printer display, the auxiliary and the synchronous ports

18 The remote monitoring system of claim 1 1 wherein the receiver circuit includes driver modules coupled to the CPU for providing alarm outputs

19 The remote monitoring system of claim 18 wherein the driver modules each have a relay decoder driver circuit including a plurality of relays having alarm contacts such that the CPU may switch the contacts in the relay decoder driver circuit to provide the alarm outputs.

20 The remote monitoring system of claim 12 wherein the receiver unit includes modem interface units for the modems with two said modems being connected to each said modem interface unit.