Computer integrated manufacturing system

What is claimed is:

1. A multilevel computerized process control system, comprising:

a first level computer system comprising at least one first computer for controlling a plurality of individual processes for producing a plurality of different products, said first level computer system comprising:

a plurality of sensor inputs for receiving process monitoring sensor signals from sensors at respective process stations,

a plurality of control outputs for providing control signals for processes to be controlled, p1 storage for storing process control parameters for processes to being carried out,

storage for storing bill of materials records containing indications of materials necessary for products being produced;

storage for storing values of said sensor signals, and

programs for producing said control signals to control said processes as a function of said sensor signal values and said process control parameters for processes being carried out;

a second level computer system comprising at least one second computer connected to said first level computer system and storing a database having a plurality of files containing process control parameters associated with different processes which may be required to be performed by said first level computer system to produce different products, said files including a process specification file containing records indicating process control parameters necessary for producing said different products and a bill of materials file containing records indicating materials necessary for producing said different products, said second level computer system:

being connected to receive scheduling information indicative of scheduled process controls to be carried out by said first level computer system to produce scheduled products,

being programmed to provide selected ones of said control parameters necessary to carry out said scheduled process controls to said first level computer system as said control parameters for processes being carried out and to provide selected records from said bill of materials file indicating materials necessary for producing said scheduled products as said materials for products being produced, and

being programmed to receive indications of said values of said sensor signals; and

a third level computer system connected to said second level computer system, said third level computer system being programmed to generate said database and transmit said database to said second level computer system and being connected to receive modification instructions for modifying records of said database, said modification instructions being contained in a modification instruction file containing information for modifying said records and information as to times at which modifications to said records are to be implemented.

2. A system as set forth in claim 1 wherein said second level computer system includes monitor drivers for displaying said values of said sensor signals on operator console monitors.

3. A system as set forth in claim 1 wherein said database includes a product specification file having records with data related to specifications of a product to be produced.

4. A system as set forth in claim 3 wherein said third level computer system stores an item master file containing records having purchasing data, and accounting data related to products produced and materials purchased.

5. A system as set forth in claim 4 wherein said third level computer system stores a revision control file containing information on revisions to any other file.

6. A system as set forth in claim 1 including an automated material delivery system for providing material to said process stations, and a further second level computer system for controlling operation of said automated material delivery system in response to commands for material received from said processing stations.

7. A system as set forth in claim 1 wherein said first level computer system comprises a lower level of computers having a plurality of identical computers programmed to carry out specific process functions, and a higher level computer connected to other first level computer systems in a communication network, said higher level computer being connected to said plurality of lower level computers and being programmed to receive process control parameters required for said lower level computers to carry out their specific process functions from said second level computer system, transmit said received process control parameters to said respective lower level computers as required for said lower level computers to carry out their programmed specific process functions, receive sensor signal values from said respective lower level computers and transmit said received sensor signal values to said second level computer system.

8. A system as set forth in claim 7 wherein said second level computer system comprises a superior level computer and an inferior level of computers, said inferior level of computers comprising a plurality of identical computers connected together in a communication network and being connected to a respective plurality of higher level computers of said first level computer network, said inferior level of computers being programmed to display said received sensor signal values on display consoles, and receive from said superior level computer and store respective portions of said database required for said lower level computers to carry out their specific process function.

9. A system as set forth in claim 1 wherein said scheduling information comprises a production schedule for a first predetermined period of time, and said second level computer system provides to said first level computer system a second production schedule which covers a second period of time shorter than said first period of time.

10. A system as set forth in claim 8 wherein said scheduling information comprises a production schedule covering a first period of time received by said superior level computer and wherein said superior level computer provides scheduling information to said inferior level computers which covers a shorter period of time and said superior level computer provides said respective portions of said database to said inferior level computers which contain process parameters required over said shorter period of time to meet said production schedule.

11. A system as set forth in claim 1 wherein said second level computer system stores a product definition file having a record for each product to be scheduled, each record of said product definition file containing information indicating all bill of material records for a particular product to be scheduled and all process control parameters for the particular product to be scheduled.

12. A system as set forth in claim 11 wherein said second level computer system accesses one of said product definition file records in response to said scheduling information indicating a product to be produced and passes the accessed product definition file record to said third level computer system.

13. A system as set forth in claim 12 wherein said third level computer system receives said accessed product definition file record and produces said control signals by determining process variable set points from said process control records.

14. A system as set forth in claim 7 wherein said third level computer comprises a plurality of individual higher level computers interconnected by a networking system.

15. A system as set forth in claim 14 wherein said networking system comprises a collision system.

16. A systemas set forth in claim 14 wherein said lower level computers are connected to said higher level computers by a second networking system.

17. A system as set forth in claim 16 wherein said second networking system comprises a polling system.

18. A systemas set forth in claim 1 wherein said second level computer system comprises a plurality of individual second level computers interconnected by a second level networking system.

19. A system as set forth in claim 18 wherein said second level networking system comprises a collision system.

20. A system as set forth in claim 1 including a common disc storage area and wherein said second and third level computer systems are connected to said common disc storage area.

21. A system as set forth in claim 1 wherein said third level computer system stores a modification file containing records, each modification order record containing a modification order number, approval data corresponding to said modification order number and change reason data indicating a reason for the modification corresponding to said modification order number.

22. A multilevel computerized process control system, comprising:

a first level computer system comprising at least one first computer for controlling a plurality of individual processes for producing a plurality of different products, said first level computer system comprising:

a plurality of sensor inputs for receiving process monitoring sensor signals from sensors at respective process stations as well as sensors for receiving indications of material levels of products in process,

a plurality of control outputs for providing control signals for processes to be controlled,

storage for storing process control parameters for processes to being carried out,

storage for storing bill of materials records containing indications of materials necessary for products being produced;

storage for storing values of said sensor signals, and

programs for producing said control signals to control said processes as a function of said sensor signal values and said process control parameters for processes being carried out;

a second level computer system comprising at least one second computer connected to said first level computer system and storing a first database having a plurality of files containing process control parameters associated with different processes which may be required to be performed by said first level computer system to produce different products, said files including a process specification file containing records indicating process control prameters necessary for producing said different products, and a bill of materials file containing records indicating materials necessary for producing said different products, and a second database storing plant production and inventory records containing inventory levels and plant production data, said second level coputer system: p1 being connected to receive scheduling information indicative of scheduled process controls to be carried out by said first level computer system to produce scheduled products,

being programmed to provide selected ones of said control parameters necessary to carry out said scheduled process controls to said first level computer system as said control parameters for processes being carried out and to provide selected records from said bill of materials file indicating materials necessary for producing said scheduled products as said materials for products being produced,

being programmed to receive indications of said values of said sensor signals and update said plant production and inventory records; and

a third level computer system connected to said second level computer system, said third level computer system being programmed to generate said first database and transmit said first database to said second level computer system and being connected to receive modification instructions for modifying records of said first database, said modification instructions being contained in a modification instruction file containing information for modifying said records of said first database and information as to times at which modifications to said records of said first database are to be implemented.

23. A system as set forth in claim 22 wherein said second level computer system also stores an operating instruction file containing information from certain records of said first database relating to operating instructions for producing said different products, and a recipe file containing information from certain records of said first database relating to components for producing said different products, and said operating instruction file and said recipe file comprise said selected ones of said control parameters provide to said first level computer system.

24. A system as set forth in claim 22 wherein said second level computer system provides material on hand displays based on information relating to material being processed provided from said first level computer system.

25. A system as set forth in claim 24 wherein said second level computer system further comprises means to permit manual adjustment of inventory levels in said second database.

26. A system as set forth in claim 24 wherein said second level computer system provides a transaction log for indicating chronological inventory events.

27. A system as set forth in claim 22 wherein said second level computer system includes means for accumulating information relating to raw material inventories and for producing a raw material inventory report indicating the inventory level of said raw materials.

28. A system as set forth in claim 22 wherein said second level computer system includes means for accumulating information relating to products produced and producing a position report indicating the inventory level of said products produced.

29. A system as set forth in claim 23 wherein said second level computer system down loads into active memory of said first level computer system recipes and operating instructions from said recipe and operating instruction file for a current run and a next subsequent run, and said first level computer system also stores a copy of said recipe file and said operating instruction file.

30. A system as set forth in claim 22 wherein said first level computer system receives and stores data relating to production based on operating day, operating shift, and operating run.

31. A multilevel computerized process control system according to claim 1, wherein said first level computer system comprises a plurality of first computers disposed in a plurality of manufacturing plants and said second level computer system comprises at least one second computer in each said manufacturing plant, and wherein said third level computer system is connected to all of said second level computers to provide centralized multi-plant control.

32. A multilevel computerized process control system according to claim 1 wherein said third level computer system is programmed to generate a master schedule and transmit said master schedule to said second level computer system as said scheduling information.

33. A multilevel computerized process control system according to claim 32 including in said first level computer system inputs for receiving signals indicative of inventory levels of materials required to produce scheduled products and wherein data indicative of material levels of products in process and inventory levels of materials required to produce scheduled products are transmitted by said first level computer system to said second level computer system, and said second level computer system generates individual schedules for the individual processes based thereon and based on said master schedule.

34. A multilevel computerized process control system according to claim 33 wherein said second level computer system is programmed to provide call outs to vendors for ordering materials required by said individual schedules.

35. A multilevel computerized process control system according to claim 32 wherein said third level computer system is programmed to receive and generate said master schedule based on data indicating a long range forecast of demand for products to be produced and data indicating long range capacity production capacity.

36. A multilevel computerized process control system according to claim 34 wherein said call outs are generated by said second level computer system by subtracting daily material requirements as determined from said individual schedules from inventory in the plant.

37. A multilevel computerized process control system according to claim 1 wherein said first level computer system comprises a plurality of computers connected to control a plurality of said individual processes in a sequential processing line.

38. A multilevel computerized process control system according to claim 37 wherein said sequential processing line is a cigarette manufacturing line.

39. A multilevel computerized process control system according to claim 38 wherein said cigarette manufacturing line includes means for conditioning tobacco to carry out a tobacco condition process as one of said sequential processes.

40. A multilevel computerized process control system according to claim 39 wherein said cigarette manufacturing line includes means for cutting tobacco to carry out a tobacco cutting process after said tobacco conditioning process.

41. A multilevel computerized process control system according to claim 40 wherein said cigarette manufacturing line includes means for making cigarette rods from cut tobacco after said tobacco cutting process to carry out a cigarette rod making process.

42. A multilevel computerized process control system according to claim 41 wherein said cigarette manufacturing line includes means for packing cigarette rods into a cigarette pack after said cigarette rod making process to carry out a cigarette packing process.

43. A multilevel computerized process control system according to claim 42 wherein said cigarette manufacturing line includes means for cartoning cigarette packs after said cigarette packing process to carry out a carton packing process.

44. A multilevel computerized process control system according to claim 43 wherein said cigarette manufacturing line includes means for palletizing cigarette cartons after said carton packing process.

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FIELD OF THE INVENTION

This invention relates to computerized control of manufacturing facilities and especially to control systems known as computer integrated manufacturing facilities in which an integrated computerized control is established from the management level through the shop floor level.

DISCUSSION OF RELATED ART

Computerized control systems have been known and widely used for a long time. In the manufacturing environment, these systems have generally been used in isolated areas to control a single machine or a single group of machines for producing a product, or used to control a line of machines in a process control. In addition, computer systems are commonly used to assist company accounting departments, sales departments, research and development departments and the like. Recently, it has been suggested that a hierarchy of control be established to integrate the various individual computer systems found in a plant. Such integration, however, has proved to be difficult and, while much has been written about the desirability of such a fully automated system, little has actually been accomplished to bring about an actual fully computerized integrated manufacturing facility.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a computer integrated manufacturing facility.

Another object of the present invention is to provide a computer integrated manufacturing facility in which a novel manufacturing specifications system is used to define and disseminate bill of materials information as well as process control specifications.

A further object of the present invention is to provide a computer integrated manufacturing system in which scheduling information is combined with the bill of material and process control data to provide precise control data for manufacturing stations on the shop floor.

Another object of the present invention is to provide a computer integrated manufacturing system in which individual management centers are established to control various functions in the plant and the individual management centers are interconnected so that they can communicate with each other.

An additional object of the present invention is to provide a computer integrated manufacturing system in which changes in specifications and process control data can be made easily, can be verified and can be disseminated to the shop floor in a timely manner according to a predetermined implementation schedule.

Yet another object of the present invention is to provide a computer integrated manufacturing system in which a plurality of levels of computers are established with communication between computers on each level as well as communication between computers on adjacent levels.

An additional object of the present invention is to provide a computer integrated manufacturing system which implements just-in-time concepts for both machine scheduling and material ordering.

In accordance with the above and other objects, the present invention is a multilevel computerized control system, comprising a first level computer system having at least one first computer for controlling a plurality of individual processes for producing a plurality of different products. The first level computer system comprises a plurality of sensor inputs for receiving process monitoring sensor signals from sensors at respective process stations, a plurality of control outputs for providing control signals for processes to be controlled, storage for storing process control parameters for processes to being carried out, storage for storing bill of materials records containing indications of materials necessary for products being produced, storage for storing values of the sensor signals, and programs for producing the control signals to control the processes as a function of the sensor signal values and the process control parameters for processes being carried out. A second level computer system is also included. The second level computer system comprises at least one second computer connected to the first level computer system for storing a database having a plurality of files containing process control parameters associated with different processes which may be required to be performed by the first level computer system to produce different products. The files include a process specification file containing records indicating process control parameters necessary for producing the different products and a bill of materials file containing records indicating materials necessary for producing the different products. The second level computer system is connected to receive scheduling information indicative of scheduled process controls to be carried out by the first level computer system to produce scheduled products, is programmed to provide selected ones of the control parameters necessary to carry out the scheduled process controls to the first level computer system as the contrl parameters for processes being carried out and to provide selected records from the bill of materials file indicating materials necessary for producing the scheduled products as the materials for products being produced, and is programmed to receive indications of the values of the sensor signals. Finally, a third level computer system is included. The third level computer system is connected to the second level computer system and is programmed to generate the database and transmit the database to the second level computer system. The third level computer system is also connected to receive modification instructions for modifying records of the database. The modification instructions are contained in a modification instruction file containing information for modifying the records and information as to times at which modifications to the records are to be implemented.

In accordance with other aspects of the invention, the second level computer system includes monitor drivers for displaying the values of the sensor signals on operator console monitors.

Furthermore, the database may include a product specification file having records with data related to specifications of a product to be produced, a bill of materials file continuing a list of materials needed to produce a product, an item master file containing records having purchasing data, and accounting data related to products produced and materials purchased, and a revision control file containing information on revisions to any other file.

An automated material delivery system may be included for providing material to the process stations, and a further second level computer system may be provided for controlling operation of the automated material delivery system in response to commands for materials received from the processing stations.

Each first level computer system may comprise a lower level of computers having a plurality of identical computers programmed to carry out specific process functions, and a higher level computer connected to other first level computer systems in a communication network. The higher level computer is connected to the lower level computers and is programmed to receive process control parameters from the second level computer system required for the lower level computers to carry out their specific process functions, transmit the received process control parameters to the respective lower lever computers as required for the lower level computers to carry out their programmed specific process functions, receive sensor signal values from the respective lower level computers and transmit the received sensor signal values to the second level computer system.

The second level computer system may comprise a superior level computer and an inferior level of computers. The inferior level of computers comprises a plurality of identical computers connected together in a communication network and is connected to a respective plurality of higher level computers of the first level computer network. The inferior level of computers is programmed to display the received sensor signal values on display consoles, and receive from the superior level computer and store respective portions of the database required for the lower level computers to carry out their specific process functions.

The scheduling information may comprise a production schedule covering a first production period which comprises a first time period. The first production schedule is received by the superior level computer and the superior level computer provides scheduling information to the inferior level computers which covers a shorter period of time and the superior level computer provides the respective portions of the database to the inferior level computers which contain process parameters required over the shorter period of time to meet the production schedule.

The invention also includes a manufacturing control system comprising a computer database system for storing information relating to products to be manufactured and processes for manufacturing the products as well as information relating to changes in the products and processes. The database system includes a product file containing detail specification records for finished and intermediate products, a process file containing records with process parameters and instructions for machines or groups of machines used for producing the products in the product file, a material file containing records with detail specification data for purchased materials, and a change order file containing information relating to proposed changes in records of the other files. The change order file contains records indicating the type of change, change approval information and the effective date of the change.

The invention also includes the method of controlling the computer integrated manufacturing system and the method of manipulating the database.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects of the present invention will become more readily apparent when the invention becomes more fully understood from the detailed description set forth below, reference being had to the accompanying drawings in which like reference numerals represent like parts throughout and in which:

FIG. 1. shows an overview of a plant to be controlled by the computer integrated manufacturing system of the present invention.

FIGS. 2a, 2b, 2c and 2d show an overview of the computer architecture used in the computer integrated manufacturing system of the present invention.

FIG. 3. shows an overview of the organization of the software systems of the computer integrated manufacturing system of the present invention.

FIG. 4. is a table showing the relationship of the access keys for the manufacturing standards system as they relate to the files of the manufacturing standards system.

FIG. 5. shows the file organization of the manufacturing standards system of the computer integrated manufacturing system of the present invention.

FIG. 6. shows the relationship of the various files of the manufacturing standards system.

FIG. 7. shows the relationship of the change order file and the revision file to the other files of the manufacturing standards system.

FIG. 8 shows a flow chart depicting the change order implementation sequence of the manufacturing standards system.

FIG. 9. shows the structure of the product definition file of the factory manufacturing standards system of the present invention.

FIG. 10. shows the structure of the configuration matrix of the factory manufacturing standards system of the present invention.

FIG. 11. shows an overall view of the scheduling functions performed in accordance with the present invention.

FIG. 12 is a block diagram showing the overall flow of information in the scheduling system of the present invention.

FIG. 13. shows a detailed view of one making and packing complex.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in relation to a cigarette manufacturing facility, it being understood that the principles and concepts described herein are also application to other types of manufacturing plants.

In order to understand the concepts of the present invention, it is helpful to understand the major functions to be performed in the manufacture of a cigarette. FIG. 1 shows a block diagram flow chart of the operations to be performed in the manufacture of a cigarette.

First, tobacco is received at the grade entry area 100. Here, grded tobacco in bales is pulled according to a pull list which is displayed on a monitor according to a stored recipe. The tobacco has been previously marked with a bar code indicating the grade of the bale. As is well known, tobacco is graded according to grade, belt, and crop year. The actual grading of the tobacco is not the subject of the present invention and will not be discussed in detail here. In general there are two types of tobacco processed. These are Turkish tobacco and domestic tobacco. These two types may require different subsequent processing and therefore may be received at different grade entry areas 100.

The bar code on the bale is read and automatically compared with a grade code stored in the recipe file indicating the grade of tobacco required. If the received bale is acceptable, it is sliced into smaller sections which are weighed so as to in feed the appropriate amount required by the recipe, preconditioned to provide an appropriate amount of moisture for subsequent delamination, and then passed to the strip condition area 102.

In strip condition area 102, the slices are delaminated in a delaminating feeder which passes the tobacco to a conditioning drum. The conditioning drum increases the temperature and the moisture level of the tobacco to be within a predetermined range. After leaving the conditioning drum, the tobacco flow is divided into two equal parallel lines. Each of these lines has a separator in which the lighter, loosened lamina is separated from the heavier, unloosened leaf by an ascending air stream. Moreover, dirt particles are separated from the lighter lamina. The heavier lamina is exposed to another conditioning process in a steam flotation chamber. This results in an additional loosening up of the tobacco.

Grade entry area 100 together with strip condition area form the receiving and blending (R&B) zone. There may be a plurality of R&B lines depending on the total amount of tobacco to be processed.

From the R&B zone the conditioned tobacco is fed to the group blended strips area 104 (GBS zone). The GBS zone comprises three infeed lines which feed 20 bins arranged in two groups of five bin pairs. The bins of the GBS zone provide intermediate storage for various tobacco blends, which are not yet final blends according to the stored recipe. The various R&B zones communicate by conveyors to the three infeed lines of the GBS zone in order to fill the GBS bins. The various bin pairs are assigned to different types of blends. For example, four of the bin pairs may contain a Burley tobacco blend, three of the bin pairs may contain a Flue Cured tobacco blend, one bin pair may contain a Maryland tobacco blend, one bin pair may contain a Turkish tobacco blend, etc.

Each bin pair of the GBS zone is connected by conveyor to feed either one of two infeed lines to the final blended strips area 106 (FBS zone). The FBS zone comprises four bin pairs which are fed with tobacco from the bin pairs of the GBS zone according to a recipe. That is, the tobacco being stored in the intermediate storage of the FBS zone is moved upon demand to the FBS zone in controlled quantities so that a final blend is obtained in each of the FBS zone bin pairs.

The final blended tobacco is passed from one of the bin pairs of the FBS zone according to the recipe to the casing area 108. The casing area comprises a casing drum into which steam, moisture and casing are provided. After being cased, the tobacco is passed to the cutting area 110 where it is cut to the proper size for the tobacco product being produced, according to the recipe. The cut tobacco is then dried and cooled in the drying and cooling area 112 and then passed to the top dressing area 114. The casing area 108, cutting area 110, drying and cooling area 112 and top dressing area 114 form the cutting and casing zone (C&C) of the process. Further details of the C&C zone are set forth in co-pending application Ser. No. 865,483, filed May 20, 1986, abandoned, and assigned to the assignee of the present invention, the disclosure of which is incorporated herein by reference thereto.

The portion of the system made up by the R&B, GBS, FBS and C&C constitutes the primary processing portion of the cigarette manufacturing process.

From the C&C zone, the tobacco is transported to the cut filler storage area 116. This area comprises a plurality of bins for storing the cut filler until it is needed for the final cigarette making step.

When needed, the cut filler is transported via conveyor to the rod making area 118 where the cigarette rods are formed. After formation of the rods, the rods are packed together usually 20 to a pack in the packing area 120. The packs of cigarettes are then packed into a carton in the carton packing area 122. The cartons of cigarettes are then packed into a case in the case packing area 124. The cases are then assembled together on pallets in the pelletizing area 126. One rod making machine, one packer, one carton packer, one case packer and one palletizer are assembled into a single making and packing (M&P) complex. A single plant may contain 72 or more such complexes. The M&P complexes are fed from bins which are themselves fed from the FBS bins. The M&P bins are connected such that three bins feed six complexes. This provides sufficient flexibility for the simultaneous manufacture of a plurality of cigareete brands even if one or more of the complexes become disabled.

Finally, the palletized product is moved to the finished goods area 128 for storage or shipment for sale.

As will be discussed in further detail below, a plant also may include an automatic guided vehicle (AGV) system comprising a plurality of guided vehicles which operate under computer control to bring materials to the M&P complexes when needed and to transport finished product to the finished goods area when the cases have been palletized. The plant also includes an automated materials storage and retrieval system known as a factory service system (FSS) which takes the form of a computerized warehouse for storing and retrieving the materials to be delivered to the M&P complexes by the AGV system.

The foregoing provides an overview of the cigarette making process controlled by the present invention. In general this comprises primary processing, making and packing and finished goods. It should be understood that the foregoing describes the activities of a single plant. However, a plurality of plants may be operating at the same time. It is also possible that some of the activities discussed above may be carried out at a first plant and some of the activities may be carried out at a second plant with the product of the first plant being shipped to the second plant for further processing. All of these possibilities are contemplated by the present invention.

COMPUTER ARCHITECTURE

FIG. 2 shows the general architecture of the computer system used in the present invention. The system includes a mainframe computer system 130 located at corporate headquarters. This computer system is referred to as the level IV system and is used to generate the material specifications, product specifications, and process specifications which are eventually used to produce product art the shop floor. The level IV system could be any mainframe but in this particular instance is shown to be an IBM computer system.

It should be noted that the term "material" is used hereafter to refer to a material which is purchased for use in manufacturing a product. A "product" is something which is manufactured even if the "product" is only used for the manufacture of another product. Accordingly, as will be discussed in more detail below, both materials and products are used in the manufacture of other products.

The level IV computer system 130 may be connected to a plurality of plants. A single plant is shown in FIG. 2 to comprise a level III computer system made up of Digital Equipment Corporation (DEC) VAX 11/750 computers 132 and 134 as well as DEC VAX 8600 computers 136, 138 and 140. The level IV system is shown to communicate to the level III system through one or more DECnet/SNA gateways at 56 KB. This communication link is served by one or more DEC PDP 11/24 computers.

The computers of the level III system communicate to each other through an ETHERNET communication link. This is a conventional collision detection type communication link provided by DEC. It is not essential that the computers of the level III system be from the same manufacturer. However, it is imperative that they be capable of communication with each other. Accordingly, by having the computers originate from the same vendor, the communication between computers is easily achieved by using vendor supplied systems.

The level III systems perform functions to be d