GB2161627A - Computer information distribution system - Google Patents

Abstract

The system comprises (a) a personally portable groundstation computer (1) and (b) at least one pocket-size personal computer (2), the groundstation and personal computers having compatible communications ports enabling the two to be connected together to electrically transfer data from the groundstation computer to the, or each, personal computer. The groundstation computer is arranged to store data items and to respond to user input to select items of data and transfer them to the personal computer via the ports and the personal computer(s) is arranged to store data items so received and selectively to display them in accordance with user input thereto. The system can thus be used for purposes such as to distribute mission information to helicopter crews. <IMAGE>

Description

SPÈCI FICATION Computer information distribution system The present invention relates to a computer information distribution system.

According to the present invention there is provided a computer information distribution system comprising (a) a personally portable groundstation computer and (b) at least one pocket-size personal computer, the groundstation and personal computers having compatible communications ports enabling the two to be connected together to electronically transfer data from the groundstation computer to the, or each, personal computer, the groundstation computer being arranged to store data items and to user input to select items of data and transfer them to the personal computer via the ports and the personal computer(s) being arranged to store data items so received and selectively to display them in accordance with user input thereto.

Preferably, the groundstation computer is equipped with a removable, non-volatile data storage means so that data can be readily loaded when the groundstation computer is turned on and so that data can be transferred between groundstations.

Preferably, such interface circuitry as may be required to interface the groundstation computer with the personal computers is located in the groundstation computer so that no special interface need be provided on the personal computers themselves.

The present computer system is intended to provide an arrangement whereby data from a centralised store of data (in the groundstation) can be transferred to individual personal computers and then accessed by their users. One example of the many applications of the system, described below in detail with reference to the drawings, is to provide mission information to flight crews of helicopters. In such an application, the transfer of information will only be required to be one-way, i.e. from the groundstation to the personal computer(s).

The personal computer user will typically require information under a number of subject headings. Typical subject headings in the case of a helicopter mission may include codes, map references, text messages, radio frequencies and so forth. Preferably the groundstation computer is suitably programmed so that suitable values for such data (whether exclusively numeric or alphanumeric) may be input, by the the operator or from storage, or a selection of data already stored may be made, so that a block of data comprising data under each of the subject headings can be readied for transfer via the interface to the personal computer(s). Some of the information may be specific to the user of a particular personal computer while other data in the block may be common, say to all the users of personal computers assigned to a particular groundstation.

The groundstation computer may include means, e.g. a reset switch, which will erase the programme and, where it is desirable, e.g.

for security reasons, also the data stored in its main memory and the associated non volatile store. Both the groundstation and the personal computer(s) may be programmed so that either their entire operation or selected parts of the software are password-protected so that data can only be viewed or manipulated by authorised personnel.

Preferably the operation of the groundstation and personal computers is menu-driven with the software of the groundstation computer checking that data under each subject heading has been assigned for transfer to the personal computer(s) before it will carry out the transfer.

The invention will be further described by way of non-limitative example with reference to the accompanying drawings in which: Figure 1 is a block diagram of a computer system embodying the present invention; Figure 2 is a plan view, with the carrying case open, of the groundstation computer of the system of Figure 1; Figure 3a shows a pocket computer which may be used as the personal computer of the computing system; Figure 3b shows a keyboard overlay which may be used with the computer of Figure 3a; Figures 4a to 4c show a typical menu tree for the groundstation computer of the system of Figure 1; and Figures 5a and 5b show a typical menu tree for the personal computer(s) of the system of Figure 1.

In the following, the invention will be described with reference to its application to the provision of mission information for helicopter flight crews. However, it will be appreciated that this is merely illustrative and the various features of the hardware, software and functioning of the system to be described may also be used in any other suitable application.

In other applications other data structures and methods of user input (e.g. by command line strings rather than menu trees) may be appropriate.

Figure 1 is a block diagram of an embodiment of the present invention in which showing a groundstation computer 1 and one of a number of personal computers 2 which may be used in association with the groundstation.

The personal computer 2 is shown as being temporarily connected via a cable 3 with an interface unit 4 in the groundstation computer. The personal computer to also includes an interface unit (not shown) electrically and protocol-compatible with the interface unit 4 of the computer system 1.

The groundstation computer 1 includes a rugged, brief case or small-suitcase-sized car rying case 10 which is preferably made of aluminium. The case 10 houses the computer unit 11 the interface unit 4, a removable data cartridge 5, a programme storage unit 6 for storing a permanent version of the programme and a power supply unit 7 which may be used, for example, to draw power from a vehicle power supply. To allow some independence a sealed lead acid battery will be included in the power supply unit 7 which may be so arranged that when the groundstation is connected to the command post supply, the battery will recharge, and all units will be supplied directly. When the command post supply is removed from the groundstation, the internal battery will provide power to the units.

The programme storage unit 6 may conveniently be a compact cassette player although it could use any other suitable non-volatile programme storage medium e.g. a magnetic disc, bubble memory or ROM, as can the data cartridge 5 although it is presently preferred that for convenience of use the data cartridge 5 utilizes non-volatile semi-conductor memory.

The carrying case 10 suitably has a sculpted insert 12 of foamed plastics or other suitable material which is cut out to receive the computer unit 11 and one or more of the personal computers 2 as at 1 3a and 1 3b. The unit may also be provided with a control panel 14 having an on/off switch and an interface outlet.

The insert 12 may further be provided with one or more receptacles such as 15 for receiving the interconnecting lead 16 for connecting the groundstation computer to the personal computer and a further receptacle such as 17 for the data cartridge (not shown).

Before describing the illustrated system in greater detail, it would be useful to describe the information handling requirements of a mission information distribution system useful for providing mission informaton to helicopter flight crewes.

At present, Communications Electronic Instructions (CEI) are distributed on paper. However, due to the volume of CEI information, a problem arises from the bulk of paper required. The paper problem is especially noticable within the Army Air Corps. During a mission aircrew may encounter several land units and will require sufficient CEI to communicate with each unit. The restricted helicopter cockpit, and the need for rapid and effective communication whilst performing normal flying tasks, does not provide aircrew with a suitable environment for a bulky paper-based information system.

Typically, a helicopter will be tasked to work with a number of formations during a day. During a mission, however, the helicopter may be re-tasked to work with other formations. The crew will therefore need to communicate on the nets of each of these formations and also on the nets of specific battlegroups or combat teams which it may be required to support.

In addition the crew may use the divisional net, and of course the Army Air Corps net.

A crew requires the following information: radio frequencies for periods 1 and 2, address groups, NIS and Call Sign Indicators (using the new voice procedure). This information is required for each formation, battle-group and combat team, where available.

Important information has to be passed in coded form. Grid references in particular may be passed over the net in code using a suitable encoding/decoding scheme.

The code may be used with vocabulary cards which give a number of digits or other indicators for each of a number of standard phrases. The code table is then used to encode the two digit number and any associated numeric or text information.

Since helicopter crews will work with several battle groups, they will require a large number of code tables. It is not feasible for these tables to be carried on paper since it would involve too high a crew workload in identifying and using each required sheet. It is desirable, therefore, that computer system 1 can handle code schemes such as or whatever other code scheme is currently in use.

Many code schemes include an authentication table which should be supported by the computer system.

There are many other types of information which the personal computers 2 may usefully store, two examples being IFF codes and Locstats. IFF codes must be changed periodically. The computers 2 can store these codes in sequence, and when requested can display the current code.

Locstats: several locations are required to be known, e.g. battle group locations, refuelling points. These are currently held on paper and may be stored, accessed and changed easily on an electronic device.

In use of the system, the hand-held personal computers 2 Information Computer will be used by the helicopter crews on missions; and the groundstation computer 1, located at the squadron command post and used to set up the mission information for the next day.

The personal computers 2 will hold CNR management information, code tables, IFF and Locstats for a day's operation. It will be used by the pilot or air gunner wearing flying gloves in the helicopter cockpit. In view of the operating circumstances, the personal computers 2 should have the following characteristics.

a) The display 21 (Fig 3A) should have the capacity for a large number of characters to allow a resonable amount of coded text to be displayed while encoding. If the display is to show two radio frequencies, then it will need at least twelve characters.

b) Th~e display should be alphanumeric.

c) Keyboard information will be alphanumeric, and so the computer keyboard 22 should have a full set of alphabetic as well as numeric keys (22A and 22B, respectively). It is desirable that the keys be programmable so that they may be used to select the functions required. Additionally, for the easy use of codes, it is desirable that the numeric keys be distinct from the alphabetic keys.

d) The total memory requirement will depend on the application in question-to implement the features discussed above it could be expected to be approximately 1 6 kbytes.

e) The computer 2 requires a data input in order to receive mission information from the groundstation computer 1.

f ) The computer 2 must be self-sufficient as far as power is concerned. Ideally it will use manganese alkaline or other long life batteries. It must also be small enough to be carried in a pocket, and should be capable of being operated with one hand.

g) Environment: the environment which will be experienced by the computer will depend on the application in question. In the application under consideration twill be used in the helicopter cockpit which will normally provide a temperate environment. In such circumstances there is no need to give it a special environmental enclosure and for carrying purposes a soft case will be sufficient. A more durable case may be required in extremes climates or rugged conditions.

h) Speed: a resonable performance is required of the computer in order to encode and decode messages using the chosen coding sheme. A popular yardstick is to decode a grid reference in less than 8 seconds.

A currently available computer suitable as the computer 2 is the Hewlett-Packard HP 71B hand held computer.

The basic HP-71B hand held computer with no additional memory provides the following desirable characteristics for the personal computer 2.

The display is a 22 character liquid crystal display, (accessing 96 character line) with full pixel addressability for graphics. Characters are 7 X 5 pixels in an 8 X 6 pixel box. The display can be tilted to improve readability.

A typewriter-like QUERTY alphabetic keyboard is provided, with separate numeric keypad. Dedicated keys are provided for ON/OFF, RUN, END LINE, space and cursor movement. Function (Shift) keys access scientific functions, lower case letters and less often used characters ($, a, etc.). All keys may be redefined to perform specific functions. The keyboard may be customised for use in the present application by use of a card overlay or face plate such as 23 shown in Figure 3B.

A flexible membrane overlay may be used instead of the card overlay 23 so as to increase the perceived size of the keys and to relabel the programmed keys.

The computer contains 1 7.5kbytes of RAM in this example. This may be increased to 33.5kbytes by the addition of extra plug in RAM modules and the memory contents are preserved when the computer is switched off.

Programs may be permanently stored in plugin ROM modules, which may be of a variety of sizes up to 96kbytes. However, other selected systems may provide other and perhaps more flexible memory expansion capabilities.

The computer in this example uses Hewlett Packard's HP-IL interface for communication with other equipment. This is a simplified serial version of the industrial standard communications protocol IEEE-488 (developed by Hewlett Packard as the GP-IB interface). Of course, in other examples an RS 232 or any other interface appropriate to the circumstances might be used.

Power is obtained either from a transformed AC supply or internal batteries. The computer requires 4 MN2400 manganese alkaline batteries. When power is low an indication will be given on the display. The computer will then have sufficient power for approximately two hours of continuous use. Batteries may be replaced while the computer is switched off, without any loss of memory contents.

In this example, each computer 2 is programmed to provide the following functions: CNR management information access Code cncoding and decoding Authentication IFF code display Locstat storage and display Many other functions may also be provide such as waypoint indicators and navigation facilities.

The keyboard will be labelled such that one key will select each of the above functions.

Other keys will be labelled to select associated subordinate functions (see Fig 3B). One key will switch the computer on and off. This is located in the lower left hand corner. When the computer is switch on it will indicate the date of validity for the mission information it contains.

CNR Management Information Access: will be invoked by the key labelled 'FMN'. For the first use of this function, the name of the first formation in the list will be displayed. Subsequent use will cause the name of the formation last acessed to be displayed (i.e. the computer will 'hold' the last formation for fast access).

The key labelled 'UNIT' will display the name of a unit (e.g. Battle Group). The computer will remember the unit last displayed. If unit information is being displayed, and then another function is selected, reselection of CNR information will cause a return to the formation, and selection of UNIT will display the current unit. This ensures that a return can be made to the unit with the minimum number of keystrokes.

The key 'S/U' will access the sub-units of a unit, should there be any. The sub-unit name will be displayed.

For each of the above categories of unit, CNR management information will be held. It will be accessed by one of the keys lableled 'FRP1', 'FRP2' or 'NI'. At all times the formation, unit or sub-unit name will be displayed.

The key 'FRP1' will cause the period 1 frequencies to be displayed. Similarly 'FRP2' will cause period 2 frequencies to be displayed.

'NI' will display net information, i.e. the call sign indicator of the unit, the address group and the NIS. These three items of information are very different in their format and are clearly distinguishable.

At the end of each line the 'spare' indicator will be displayed. This is the call sign indiator for the Army Air Corps in support.

Two keys which may also be used with these functions are the text scrolling keys 't' and '#'. these allow the operator to scroll through the displayed information unit by unit. If period 1 frequencies are being displayed, then use of the scroll keys will cause period 1 frequencies for other units to be displayed.

If sub-unit information is being displayed, then scrolling will be restricted to the subunits of the relevant unit. If unit information is being displayed, then scrolling will be restricted to the units of the associated formation and if formation information is being displayed, scrolling will be restricted to formations.

Encoding and Decoding: One key labelled to indicate the name of the code in use will select the coding function. Two other keys wil be labelled 'ECN' and 'DEC' to perform the encoding and decoding functions respectively.

The code sheet selected will be that for the current battle group, the name of which will be displayed. If no code sheet is available for the current battle group, then a message stating this will be displayed. Standard Operation Procedures for the use of the code scheme in use will be followed.

Authentication: each BACTO sheet contains an authentication table. This will be accessed by the key labelled 'AUTH'. The operator will enter the two figure authentication challenge code. A response to this will be displayed if the entry has not been used. Otherwise it will be indicated as used. If the authentication challenge selected has already been used then it will be possible to use the scroll keys to move the next available authentication. A key labelled 'ACK' will cancel this entry to prevent its re-use.

IFF Code Display a key labelled 'IFF' will display the IFF code for the current time period, with the time of the start of the period.

Locstat Storage and Display: a facility will be provided to store and display Locstats.

Initially some Locstats will be established in the command post and loaded into the Mission Information Computer from the Groundstation. When the key labelled 'Locstat' is pressed, the first entry will be displayed. The display will give the Locstat number, an indication of what the Locstat refers to (e.g. the name of Battle group or FARP) and the grid reference.

Use of the scrolling keys '"' and '#' will display other entries.

Another key labelled 'Change' will allow the operator to amend the entry. Each entry will be free text and can be prepared in any format, so that any label may be used.

Mission Information Loading: a key sequence will be entered to enable to the computer to load mission data from the groundstation computer.

Emergency Erasure: the procedure to be followed to erase the memory contents will be to switch the computer on and then remove the batteries. This will result in instant erasure.

The groundstation computer will be situated in the command post, and is used for the daily loading of the computers 2.

The groundstation computer 1 will be used to prepare the CNR Management Information, code tables, IFF codes and Locstats for the Mission Information Computers for the next day's missions. This may be achieved manually or by using an optical reader or other suitable device.

In the case of the Army, the necessary information will be available on the paper SCAN lists, and will be entered manually and then the personal computers 2 will be loaded individually via the wire link 2.

The Army CEI is available in books of paper. The simplest means of entering the information is via the QUERTY keyboard 31 of the groundstation computer unit 11. An alternative would be to use an optical character reader, but the quality of printing of the SCAN lists is currently not high enough for reliable results and many errors could therefore results.

The display 32 is preferably a multiline display, since tables of information must be entered.

Memory is required for the Groundstation programs and the mission information. The memory contents must be preserved while the computer is switched off. Information for at least one day will be entered and stored. The memory requirements for mission information will therefore be the same as that for the Mission Information Calculator.

The memory required for program storage is probably something in excess of 20kbytes.

The groundstation computer 10 will be used, stored and transported in a command post vehicle (e.g. Sultan APC). It will therefore have to be rugged to withstand the dropping and bouncing it is likely to receive. Power may be obtained from the vehicle's 24V DC (nominal) supply by the power supply unit 7.

The computer 10 will be required to store and retrieve data, and send data to a Mission Information Computer. These activities are generally not time hungry, and so speed is not a critical factor.

The computer 11 must have a data output in order to send the mission information to each personal computer 2.

A suitable currently available computer for use as the computer unit 11 is the NEC PC8201 portable computer with 48kbytes of memory (expandable to 64K), altough other computers may be more suitable in other applications of the invention. In the NEC PC8201, the memory contents are preserved when the computer unit is switched off. This computer has a liquid crystal display of 8 lines X 40 characters liquid crystal display, with full pixel addressability for graphics.

Characters are 7 x 5 pixels in an 8 X 6 pixel box. The display can be tilted to improve readability.

A memory cartridge, in this example of 32 kbytes may be plugged into the computer and then loaded and removed. The cartridge can then be transported to another location where it can be used to load data into another groundstation. This may be useful for distribution of mission information (the cartridge has a capacity of 32kbytes).

This computer has a typewriter-like QWERTY keyboard with numerics on line above alphabet keys and dedicated keys for cursor control and upper/lower case lock.

Using other computers, an alphabetic keyboard might be used.

A variety of input/output interfaces are available. In this example the parallel output interface (centronics printer type) will be used to transmit data to a mission information computer via the interface unit. A suitable interface unit will be provided to convert the parallel output data interface from the computer unit to the serial HP-IL interface used by the HP-71B hand held computers.

An unmodified Hewlett Packard HP82166A HP-IL/GPIO converter, and HP82401 HP-IL interface will comprise the interface unit.

An NEC PC-8281A Data Recorder will be used as the programme storage unit 6 to hold a permanent version of the groundstation programs. The programs will be stored on a cassette tape.

Summary of Groundstation Units Components Computer Unit. IX NEC PC 8201 48kbytes RAM portable computer.

Interface Unit.

1 X cable connecting to computer unit.

1 X HP-82166A HP-IL/GPIO converter 1 X HP-82401A HP-IL interface Programe Storage Unit.

1 X NEC PC 8281A Data Recorder 1 X cable to connect to computer unit Power Supply Unit.

1 X Groundstation power supply unit 1 set of leads to supply each unit Case.

Each computer system will comprise a groundstation computer 1 and a sufficient number of personal computers 2 to equip a Squadron.

The SCAN lists are used to enter the information into the Groundstation first of all.

The Groundstation computer 1 is used to load mission information into the personal computers 2. In order to do this, the information must first be entered into the Groundstation computer unit 10.

When the groundstation computer is programmed so that when switched on, a menu will be displayed on the computer screen. The menu will list a set of options against a number index. The desired option is selected by pressing the appropriately numbered key.

Figures 4A-4C show the menu trees which may be provided from the initial menu to enable the desired information to be set up, or selected, for transfer to the personal computers 2.

Selection of a particular option may cause another menu to be displayed, giving a new set of options. Selection of the new option is made in a similar manner. Completion of an operation will cause a return to the menu from which it was selected.

One key will terminate the current menu when no further action is desired. This will cause a return to the menu from which the current menu was accessed.

Each groundstation 1 may be either a master groundstation or a relay groundstation.

As a master groundstation 1, mission information may be entered, and the personal computers 2 may be loaded manually or using a device such as an optical reader. Additionally the mission information may be stored in the data cartridge which may then be transported to another command post, where the data may be loaded into a slave groundstation computer 1.

As a slave groundstation, mission information would normally be entered in bulk from the data cartridge. The information can then be edited as desired. Mission information may also be entered through the keyboard to add to that loaded from the data cartridge.

In this example, the following functions will be provided by the software of the groundstation computer 10: 1) Setup CNR management information.

2) Setup code Tables.

3) Setup IFF codes.

4) Setup Locstats.

5) Store Mission Information into data cartridge.

6) Load Mission Information from data cartridge.

7) Load Mission Information Computer.

Setup CNR Management Information:-when this option is selected from the main menu on the display another menu will be displayed listing the various tables for CNR Management Information which can be updated within the new day's information.

Unit Names Table. One table will contain the names of the units for which CNR information will be stored. A maximum of forty entries will be permitted, and names may be added to or deleted from the table in any position. A name will be entered with an indication of whether it relates to a formation, unit or sub-unit. Since the screen will not be large enough to display the whole table, the scrolling keys '#' and '#' may be used to display earlier or later entries as necessary. If '#' is pressed the previous entry will become the current entry. If the current entry is at the top of the screen the table wil scroll down one line, displaying the new current entry. If '#' is pressed, the next entry will become the current entry.If the old current entry is at the bottom of the screen, the table will scroll up one line to display the new current entry. This table establishes the hierarchy of units, which is used by the personal computers 2 for fast access to information.

Period 1 Frequencies Table: selection of this table will permit the operator to enter the VHF radio frequencies for period 1 (midnight to midday). The frequencies will be entered against the units entered into the unit names table. Up to two frequencies may be entered for each unit.

The scrolling keys '#' and '#' may be used at any time to display any section of the table, of to select another entry as the current entry, as with the unit names table.

Period 2 Frequencies Table: selection of this table will permit the operator to enter the VHF radio frequencies for period 2 (midday to midnight). This information is entered in a manner similar to that for period 1 frequencies.

Address Groups Table: This table is selected in order to enter address groups. The information is entered in a manner similar to that for period 1 frequencies.

NIS Table: NIS is entered by selecting the NIS table. The information is entered in a manner similar to that for period 1 frequencies.

CSI Table: this table is selected when the operator wishes to enter call-sign indicators.

The information is entered in a manner similar to that for period 1 frequencies.

Setup code Tables: in this example, a maximum of ten code tables may be entered. To simplify Mission Information Computer use, each code table will be associated with a unit from the Unit Names table.

Select Units: when the Setup code Tables function is selected, the unit names will be displayed. Any entry may be made against not more than ten names to show that a code table will be entered for that unit. The list of entries will be preserved, and entries may be added and deleted as necessary.

Setup Tables: each table may be entered when required. The key settings will be entered first of all. The cipher alphabets will then be entered. This will be followd by the spelling box, and finally the authentication table. A check will be made for duplication of characters when the table sections are entered. A table format will be presented, and the information will be entered into this table.

The scrolling keys may be used to move to other part of the table to connect erroneous entries.

Setup IFF Codes: this function is selected in order to enter the 24 IFF codes for the day.

Each code will be entered against the given start of time period.

Setup Locstats: Locstats may be entered or amended during a Mission. However some Locstats will be known in advance (e.g. unit locations). These may be entered into the groundstation computer by selecting this function.

The Locstat number, and space for text, will be displayed. The scroll keys may be used to select other Locstat entries. Previously stored Locstats are preserved.

Store Mission Information into Data Cartridge: This function is selected if the Groundstation has assumed a master groundstation role. The CNR Management Information, code Tables, IFF codes and Locstats are transferred into the data cartridge which is plugged into the socket.

Load Mission Information from Data Cartridge: this function is selected on a slave groundstation to load CNR management information, code tables, IFF codes and Locstats from a data cartridge plugged into the socket.

The data cartridge would have previously been loaded from a master groundstation.

Load Mission Information Computer: once all the tables have been entered, this option may be selected to load Mission Information Computers. If as in this example the groundstation provides only one output, each Mission Information Computer will be loaded separately. It will be connected to the Groundstation by the wire link 3 and a special key sequence will be entered on the personal computer 2 to prepare it for loading. The special key sequence is necessary to prevent accidental access to this function. Of course, if the groundstation can provide more than one output, a number of personal computers may be loaded simultaneously.

The Groundstation computer 11 will then transmit mission data to the personal computer 2 via the wire link.

When transmission has completed, the personal computer 2 will switch itself off. It can then be unplugged, and another computers 2 plugged in for loading.

The groundstation computer 11 will ask if another computer 2 is to be loaded. When all computers 2 have been loaded a negative response to this question will cause a return to the main menu.

Emergency Erasure: the contents of the groundstation computer memory are preserved by an internal nickel cadminum rechargeable battery. The battery is charged from the main supply. To clear the memory, a switch is provided which will off turn the internal battery.

As mentioned above, a data cartridge may be used to transfer bulk mission data from one groundstation computer to another. The Data Cartridge in this example is an unmodified NEC PC 8206A RAM cartridge, which can hold 32kbytes of information. The memory contents are preserved by an internal battery.

The personal computer 2 may be provided with an accessory to remind the operator to carry out a task periodically. In the present case, one such task is the updating of the IFF codes.

IFF codes must be changed every half hour.

It can sometimes be difficult due to pilot workload to remember to change the code while flying due to the workload. For this or a similar purpose (i.e. to remind the operator to carry out a particular task periodically) the computer 2 may be provided with an accessory in the form of a device having a manually operable switch such as a push button and a light. The device contains timing circuitry arranged so that every half hour the light will flash, indicating that the IFF code must be changed. The push button switch will cancel the flashing light, but it will not reset the timing period. The device may be mounted in its own box, or it may be mounted on the computer 2 (e.g. fitted in the card reader compartment of the HP71 B) so that the light and cancel button are on the top face of the computer 2. The device may include a third, concealed, button will reset the timing period when required. This will be an infrequent operation since an accuracy of a few seconds a day can be achieved. Power may be obtained for the device from the computer batteries. Otherwise the warning device will require its own power supply.

As mentioned above, although the invention has been described with reference to its application as a mission information distribution system for helicopter crews, the invention can be used in a wide variety of other applications. In such applications the techniques and procedures described above may be used in an analogous fashion to their use in the mission information distribution system described above or other techniques and procedures may be used within the scope of the present invention according to the requirements of the specific application under consideration.

Claims (9)

1. A computer information distribution system comprising (a) a personally portable groundstation computer and (b) at least one pocket-size personal computer, the groundstation and personal computers having compatible communications ports enabling the two to be connected together to electronically transfer data from the groundstation computer to the, or each, personal computer, the groundstation computer being arranged to store data items and to respond to user input to select items of data and transfer them to the personal computer via the ports and the personal computer(s) being arranged to store data items so received and selectively to display them in accordance with user input thereto.

2. A computer information distribution system according to claim 1, wherein the groundstation computer is provided with a removable, non-volatile data storage means and is arranged to as to retrieve the data item to be transferred to the personal computer(s) from the non-volatile storage means.

3. A computer information distribution system according to claim 1 or 2, wherein the groundstation computer includes means which will erase the programme and/or the data stored in its main memory and/or the nonvolatile storage means, if provided.

4. A computer information distribution system according to claim 1, 2 or 3, and including interface circuitry to interface the groundstation computer with the personal computer(s), the interface being located in the groundstation computer.

5. A computer information distribution system according to any one of the preceding claims wherein the groundstation computer is suitably programmed so that suitable values for data may be input, by the the operator or from storage, or a selection of data already stored may be made, so that a block of data comprising data under each of the subject headings can be readied for transfer via the interface to the personal computer(s).

6. A computer information distribution system according to any one of the preceding claims, wherein the groundstation and the personal computer(s) is/are programmed so that either their entire operation or selected parts of the software are password-protected so that data can only be viewed or manipulated by authorised personnel.

7. A computer information distribution system according to any one of the preceding claims, wherein the operation of the groundstation and personal computer(s) is menudriven with the software of the groundstation computer checking that data under each subject heading has been assigned for transfer to the personal computer(s) before it will carry out the transfer.

8. A computer information distribution system according to any one of the preceding claims in which the groundstation computer is fitted into a carrying case, the carrying case having storage space for at least one of the personal computers.

9. A computer information distribution system constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.